The analyses of rainfall and evaporation of years in Northwest Liaoning Province showed t hat the significant difference between rainfall and evaporation is one of the important reasons for drought taking place in spring.The drought degree can be scaled by means of humidit y coefficient(0.33).Based on the coefficient.t he empiric frequency of 0.33 is calculated for every season in 20 years.The result showed that the distributing frequency of 0.33 is highest in summer and 85.71% in aut umn.Such a state can provide a good chance for taking the cover measure to control soil moisture in successive seasons.The control measures of deeply loosening soil in summer and plastic film used in aut umn can improve rainfall infiltration into soil and provide sufficient moist ure for seeding in next spring.