Abstract: In order to explore the succession of fungal community and key physicochemical properties in the fermentation process of Sichuan sun vinegar, the physicochemical properties and fungal communities of vinegar fermented grains were analyzed by national standard method and high-throughput sequencing technology. At the same time, the redundancy analysis was carried out combined with fungal community and physicochemical properties to find out the key physicochemical properties affecting the change of fungal community. The results showed that with the fermentation, the pH of vinegar fermented grains decreased, the moisture and temperature remained stable, the total acid and ammonia nitrogen content increased first and then remained stable, and the reducing sugar content increased first and then decreased. The results of high-throughput sequencing showed that there were 9 phyla and 299 genera involved in the succession of fungi during the solid-state fermentation of Sichuan sun vinegar. Pichia and Lichtheimia were the dominant fungi. Through cluster analysis, the solid-state fermentation process could be divided into three stages (the first fermentation stage, days 1~8, the second fermentation stage, days 9~12, the third fermentation stage, days 14~16). The results of redundancy analysis showed that ammonia nitrogen and total acid were the main factors affecting the fungal community. Ammonia nitrogen and total acid were negatively correlated with fermentation days 1~8, and positively correlated with the fungal community at days 9~16 of fermentation. This study revealed the diversity, succession and influencing factors of fungal communities in the solid-state fermentation process of sun vinegar, which laid the foundation for mastering the variation law of fungi in the solid-state fermentation process and the subsequent association with flavor substances.