The oriental fruit fly, Bactrocera dorsalis (Hendel), is a destructive pest in mango cultivation. Here, we monitored the annual population dynamics of B. dorsalis over the past 3 years from 2020 to 2022 in Yuanjiang, Yunnan, China, and analyzed the correlation between the population change of B. dorsalis and the climatic factors. The results showed that B. dorsalis occurred all the year during the monitored periods. In the mango orchards, B. dorsalis showed low population in winter and high population in summer. There were 2 rapid population growth periods every year in Yuanjiang. The population of B. dorsalis increased significantly in March, then decreased or slowed down in April to May. The population increased rapidly again in June and reached a peak in July. Then, the population dropped and reached the lowest level in December and January of the following year. There was a positive correlation between the B. dorsalis populations and mean monthly maximum temperature, mean monthly minimum temperature and monthly mean temperature. Monthly precipitation, monthly sunshine hours, monthly average relative humidity and monthly minimum relative humidity had little effect on the occurrence of B. dorsalis. The stepwise regression analysis indicated that the monthly mean air pressure was the major factor affecting the B. dorsalis populations. Monthly mean air pressure and monthly mean temperature are the key factors that affect the population dynamics of B. dorsalis. This study provids a theoretical basis for the prevention and control of B. dorsalis of important economic crops such as vegetables, melons and fruits in Yuanjiang County or areas with the same climate.