Abstract：Remote sensing technology can be used to obtain accurately the variation of Surface Latent Heat Flux(SLHF), therefore, can serve as a means for long-term monitoring of SLHF for tectonic activities and earthquakes(EQ). In this paper, the SLHF data from NCEP are used to analyze the variation of latent heat before Qinghai Haixi Ms 6.4 earthquake on August 28, 2009 and its aftershocks. Several conclusions are drawn. (1) SLHF anomaly started to appear around the epicenter 6 days before the main shock. Then it continued to develop in intensity and extent, and moved to the coming epicenter. It disappeared when the main shock came. The maximum SLHF reaches 70W/m2. (2) SLHF anomaly also appeared before aftershocks, but in a different spatio-temporal evolving process. The evolving processes are multi-revolving with cycling features. (3) There is a good spatial corresponding relation between SLHF anomalies and the epicenters. The strong abnormal area corresponds to the main shock, while a weak abnormal area corresponds to aftershocks. Particularly, the SLHF anomaly is located exactly at the coming epicenter in Dulan aftershock. This case implies that SLHF anomaly before earthquakes should be a Lithosphere-Coversphere-Atmosphere (LCA) coupling effect in the earthquake preparation period, especially, in the impending-earthquake process. The features of SLHF anomaly before the main shock and aftershocks in seismic active regions might be important in future researches, and can be used in earthquake monitoring, prediction, hazard warning and disaster reduction.