The invention relates to a method for prolonging alkene epoxidation stable operation time. Specifically, under alkene oxidation reaction conditions, alkene and an oxidizing agent undergo contact reaction with a catalyst on a fixed bed. The method is characterized by comprising the steps that whenever index (a) the conversion rate of the oxidizing agent drops and reaches 90% in the reaction process, and/or index (b) the selectivity of the target product oxidized alkene drops and reaches 92%, the charging space velocity of alkene is enhanced at an amplitude of 0.01-2.0h<-1>/d, so that when index (c) the conversion rate of the oxidizing agent rises and reaches 94%, and/or index (d) the selectivity of the target product oxidized alkene rises and reaches 94%, the charging space velocity of alkene is maintained. The method can keep the conversion rate of the oxidizing agent and the selectivity of oxidized alkene in a high range in the reaction contact process, , simultaneously delays deactivation of the catalyst, further prolongs the total life of the catalyst, and lengthens the total running time.