By use of the key time method for studying catastrophic laws,this paper deals with the influence of drought and higher temperature on the outbreaks of the Oriental Migratory Locust(Locusta migratoria manilensis Meyen).Results show that the precipitation less than normal in April(drought) is one of main induction factors,which causes plagues of the pest.Moreover,the regionally averaged rainfall in April plays more important role in the outbreak of summer locusts than in that of autumn locusts.The temperature higher than normal in November also contributes to the outbreak of the next summer locusts.