[Objective] The paper was to explore the population dynamics of Obolodiplosis robiniae( Haldemann).[Method] The spatial distribution of mature larvae of O.robiniae and the damage regularity of its first generation larvae on leaves of locust were studied in Fangshan District of Beijing City.[Result] The spatial distribution of mature larvae of O.robiniae in the forest was significantly higher than those in forest edge and periphery of forest edge.The attack of the first generation larvae was mainly concentrated in the lower part of tree crown.[Conclusion] The study provides theoretical basis for the effective control against O.robiniae. [Objective] The paper was to explore the population dynamics of Obolodiplosis robiniae (Haldemann). [Method] The spatial distribution of mature larvae of O. robiniae and the damage regularity of its first generation larvae on leaves of locust were studied in Fangshan District of Beijing City. [Result] The spatial distribution of mature larvae of O.robiniae in the forest was significantly higher than those in forest edge and periphery of forest edge. The attack of the first generation larvae was mainly concentrated in the lower part of tree crown . Conclusion The study provides theoretical basis for the effective control against O.robiniae.