According to measured data of Φ20cm evaporator, E601 evaporator and 20m2 evaporation pool in the key test station of modern water-saving irrigation Corps，the paper analyzed the evaporation characteristics between evaporation pools and the variation rule of conversion coefficients of the year.The conversion coefficient of water surface evaporation presents the increase trend month by month in period of non glacial . Through the correlation analysis to each evaporator evaporation,it got the result that the correlation coefficient of 20m2-E601 evaporator is 0.996 and that of 20m2-Φ20cm is 0.978.The relativity of both evaporators is significant.The results can provide reference for water balance research,water resources evaluation and the calculation of ecological water requirement in Manas river basin.Meanwhile,aimed at the little precipitation but large evaporation in arid region of northwest China,the test took the method of covering polystyrene foam board on the surface of water so as to reduce water evaporation.The result shows that the reducing rate of average water surface evaporation from May to November is up to 51.25%. The research can provide the theory basis for efficient utilization of water resources in arid areas.