The interdecadal, interannual and seasonal evaporation variations are analyzed on the basis of the available observation data from 1961 to 2004 from eight stations over Shangqiu. The results show that although the annual mean air temperature showed an increasing trend over the past 44 years, the evaporation of the same time showed a remarkable decreasing trend, which passed the statistical test with a significant level of 99%. The evaporation variation is most obvious in spring, and least in winter. Compared with the 1960s and the 1970s, the annual pan evaporation rate in the 1980s and the 1990s decreased by about 34 mm. The cause is directly correlated to the decreased average wind speed and sunshine.