Using monthly CRU precipitation and evapotranspiration data in Vakhsh River basin of Tajikistan from 1970 to 2013,applying methods such as the empirical mode decomposition (EMD) and wavelet analysis,the spatiotemporal variation of surface humid index and its correlation with precipitation was analyzed. The results showed as follow:① The annual,spring and winter surface humid index of Vakhsh River basin presented relative humidification trend,especially more significant in upper river. Whereas,the Vakhsh River basin presented relative acidification trend during past 44 years. Moreover,the humidification and acidification trend have significantly regional difference. ② The river basin relative driest in 1970s and wettest in 2000s. The area of relative wetter region increased continuously from 1970s to 2000s and reached the maximum in 2000s. ③ Annual and seasonal surface humid index all have inter-annual and inter-decadal scales variation. The main period of annual seasonal surface humid index are 4 years and 16 years,4 years,8.5 years and 26 years in spring,10 years in summer,10 years and 22.5 years in autumn,6 years,15 years and 30 years in winter. ④ Annual precipitation have significantly positive correlation with annual surface humid index,especially more closely inter-annual scales variation during 1970s, and all very closely in inter-annual and inter-decadal scales variation from 1980s to 2000s. Whereas,annual evapotranspiration have significantly negative correlation with annual surface humid index,especially more significant after 1985. This paper can provide reference for the relative research about wet and dry in river basin and raise the ability of mitigating the potential negative effect of climate change.