To understand the quality of mature forest of Zunyi,Southwest China's Guizhou Province,this paper chooses data of the fourth forest resource planning and design survey in the province,tries to organize and analyze the small-class data of the city.It selects average DBH,average tree height,hectare volume,tree species structure,canopy density,comprehensive vegetation coverage,slope and soil layer thickness to establish the quality evaluation system,construct the matter-element model for forest quality evaluation and evaluate the forest quality of Zunyi for the first time.By summarizing and analyzing the results of quality evaluation,the study concludes that the area proportion of "poor,medium,good and excellent" grade of mature forest quality in Zunyi was 1.56%,45.72%,45.87% and 6.85%,respectively.Forest quality of Yuqing,Fenggang,Bozhou are relatively better among districts and counties as their mature forest area above medium level is as high as 60%.From the perspective of forest category,the quality of commercial forest is the best,followed by local public welfare forest.In general,the quality of mature forests in Zunyi is mainly in "medium" and "good" level,with only 6.85% of "excellent" level.The results show that there is a large space scope for the improvement of the quality of mature forest in Zunyi.Scientific and reasonable management measures can be formulated to improve the forest quality in the future management practice,so as to improve the forest quality.