The NCEP/NCAR reanalysis Ⅱ datasets are used to investigate the spatial and temporal variations of the Latent Heat Flux (LHF) over the Pacific from 1979 to 2010, as well as its relationship with summer precipitation in the Huanghuai region. Results show that both of the climatological and variance fields of LHF have clear seasonal changes. The extreme value centers in the climatological fields are also the regions with larg variability. In addition, the seasonal LHF fields are analyzed through EOF analysis, and it is conclued that there existed an abrupt climate change in the spring LHF field around 1997, as well as in summer. In autumn and winter, the abrupt change happened before 1995. Summer precipitation index of the Huanghuai region was defined to investigate the key areas of LHF, and it is found that prespring LHF fields were closely related to precipitation. Key areas of the spring LHF field were over the middleeastern Pacific between 10°N and 20°N and the eastern tropical Pacific, and their relationships with atmospheric circulation show that when the LHF over the two regions mentioned above increases in spring, geopotential height anomaly both at 500 hPa and 850 hPa in summer over the western coast of Pacific displays a distribution pattern of “positivenegativepositive,” and there will be more precipitation in the Huanghuai region.