Abstract: Based on daily average temperature, maximum temperature and relative humidity data from 87 weather stations in Jiangxi Province, this paper analyzed climatic features of high temperature and low humidity during physiological fruit drop of navel orange, and examined the relationships between days of high temperature and low humidity with western Pacific subtropical anyticyclone to find out the cause of drought during physiological fruit drop of navel orange. The results showed that days of high temperature and low humidity showed an increasing trend in Jiangxi from 1981 to 2013, and had a significant increase in 2000s, but no significant increase was observed before 2000. The high temperature and low humidity-prone areas were located in southern and northeastern of Jiangxi. The Mann-Kendall test results showed that there were abrupt changes of high temperature and low humidity in the end of 20^th century. The days of high temperature and low humidity after 2000 was 2.4 days more than that before 2000. There was a close relationship between days of high temperature and low humidity with western Pacific subtropical anyticyclone. The days of high temperature and low humidity increased dramatically when western Pacific subtropical anyticyclone ridge shifted northward in March and eastward in May.