| Challenger Liuzhou | 10/21 04:40 | 24 | [348] Νίκολας Μπαριέντος v Φαγίνγ Σούν [388] | 6-4,3-6,7-6 | |
| Challenger Ningbo | 10/15 08:10 | 25 | [101] Αλεχάντρο Νταβίντοβιτς Φοκίνα v Φαγίνγ Σούν [386] | 6-7,6-2,6-4 | |
| Challenger Ningbo | 10/14 05:55 | 24 | Σιντάρο Ιμάι v Φαγίνγ Σούν | 4-6,4-6 | |
| ΑΤP Σανγκάη | 10/05 04:00 | 45 | [65] Μάρκο Κετσινάτο v Φαγίνγ Σούν [381] | 6-3,6-7,6-2 | |
| Τσάλεντζερ Σανγκάη | 09/10 05:40 | 25 | [394] Φαγίνγ Σούν v Χιρόκι Μορίγια [232] | 2-6,7-5,2-6 | |
| Τσάλεντζερ Σανγκάη | 09/09 03:55 | 24 | [330] Έβαν Κινγκ v Φαγίνγ Σούν [395] | 2-6,6-7 | |
| Challenger Jinan | 09/02 07:40 | 24 | [354] Ζε Ζανγκ v Φαγίνγ Σούν [395] | 6-3,6-4 | |
| Challenger Baotou | 08/27 03:40 | 25 | [395] Φαγίνγ Σούν v Γιαν Μπάι [222] | 4-6,3-6 | |
| Challenger Baotou | 08/26 03:55 | 24 | Χάνγι Λιού v Φαγίνγ Σούν | 4-6,1-6 | |
| Τσάλεντσερ - Κόρντενονς | 08/12 15:00 | 24 | [375] Τζέρεμι Τζαν v Φαγίνγ Σούν [389] | 6-3,6-2 | |
| ITF M25 Βογκάου | 08/07 08:00 | 25 | [392] Φαγίνγ Σούν v Γιάροσλαβ Πόσπισιλ [382] | 2-6,6-7 | |
| ITF M25 Qujing | 07/14 02:30 | 29 | [281] Φαγίνγ Σούν v Γιαν Μπάι [367] | 3-6,1-6 | |
| ITF M25 Qujing | 07/13 02:30 | 28 | [308] Τσουνγκ-Χούα Γιανγκ v Φαγίνγ Σούν [281] | 6-7,6-7 | |
| ITF M25 Qujing | 07/12 02:00 | 27 | Φαγίνγ Σούν v Τζόναθαν Μρίντχα | 7-6,6-1 | |
| ITF M25 Qujing | 07/11 03:25 | 26 | Φαγίνγ Σούν v Καζούμα Καβάτσι | 6-2,6-3 | |
| ITF M25 Qujing | 07/10 05:55 | 25 | Φαγίνγ Σούν v Λι-Βέι Ταν | 6-2,6-0 | |
| ITF M25 Kunshan | 07/07 01:30 | 29 | [308] Τσουνγκ-Χούα Γιανγκ v Φαγίνγ Σούν [281] | 2-6,2-6 | |
| ITF M25 Kunshan | 07/06 01:30 | 28 | Φαγίνγ Σούν v Haitong Xia | 7-6,6-2 | |
| ITF M25 Kunshan | 07/05 01:30 | 27 | Ρετ Πούρσελ v Φαγίνγ Σούν | 3-6,6-7 | |
| ITF M25 Kunshan | 07/04 01:30 | 26 | Soichiro Moritani v Φαγίνγ Σούν | 1-6,0-6 | |
| ITF M25 Kunshan | 07/02 08:05 | 25 | Τσούχαν Γουάνγκ v Φαγίνγ Σούν | 3-6,1-6 | |
| ITF M25 Γιντσουάν | 06/29 02:00 | 27 | [367] Γιαν Μπάι v Φαγίνγ Σούν [282] | 6-4,7-5 | |
| ITF M25 Γιντσουάν | 06/28 06:40 | 26 | Λι-Βέι Ταν v Φαγίνγ Σούν | 0-6,4-6 | |
| ITF M25 Γιντσουάν | 06/28 03:20 | 25 | Yecong Mo v Φαγίνγ Σούν | 4-6,3-6 | |
| ITF M25 Hengyang | 06/23 02:00 | 29 | [282] Φαγίνγ Σούν v Χάρι Μπουρσιέρ [407] | 6-7,1-6 | |
| ITF M25 Hengyang | 06/22 03:00 | 28 | Τσουνγγκ-Χάο Χουάνγκ v Φαγίνγ Σούν | 2-6,3-6 | |
| ITF M25 Hengyang | 06/21 03:15 | 27 | Garrett Johns v Φαγίνγ Σούν | 0-6,1-6 | |
| ITF M25 Hengyang | 06/20 03:00 | 26 | Λορέν Ροσέτ v Φαγίνγ Σούν | 1-6,4-6 | |
| ITF M25 Hengyang | 06/19 05:00 | 25 | Yecong Mo v Φαγίνγ Σούν | Retired | |
| ITF M25 Λούζου | 05/31 02:00 | 27 | Τζίε Κούι v Φαγίνγ Σούν | Retired |
Sun Fajing (Chinese: 孙发京; pinyin: Sūn Fājīng; Mandarin pronunciation: [swə́n fá tɕíŋ]; born 3 October 1996) is a Chinese tennis player.
Sun has a career high ATP singles ranking of world No. 351 achieved on 10 February 2020. He also has a career high ATP doubles ranking of world No. 181 achieved on 26 February 2024. He has reached 13 career singles finals posting a record of 5 wins and 8 losses, all coming on the ITF Futures tour. Additionally, he has reached 31 doubles finals posting a record of 16 wins and 15 losses, which includes 2 ATP Challenger Tour doubles titles.
Sun made his ATP main draw debut at the 2016 Chengdu Open, where he was granted a wildcard entry in the doubles draw alongside compatriot He Yecong. They were defeated in the first round by Raven Klaasen and Rajeev Ram in straight sets 4–6, 5–7.
The following year, he was again given a wildcard at the 2017 Chengdu Open with partner Te Rigele, and again he would lose in the first round to Nenad Zimonjic and Santiago Gonzalez in straight sets 4–6, 4–6.
In his third main draw appearance, he and partner Zhizhen Zhang were given a wildcard entry into the doubles draw of the 2018 ATP Shenzhen Open but lost in the first round to Marcin Matkowski and Nicholas Monroe 4–6, 2–6.
His fourth and most recent ATP appearance (also his third at the tournament) was a wildcard entry into the doubles draw of the 2019 Chengdu Open pairing up with Wang Aoran, and to round up an 0–4 record he lost to Dominic Inglot and Austin Krajicek 1–6, 6–0, [8–10].
He was given a wildcard at the 2023 China Open (tennis) partnering Zhou Yi (tennis). He received also a wildcard in doubles partnering Li Zhe (tennis) at the 2023 Rolex Shanghai Masters.