Abstract: The ovarian development, maturation and spawning in grass prawn, P. monodon from grow-out adults in the earth ponds could effectly be induced under the laboratory cunditions. By adopting the technques of unieyestalk ablation and/or exposed in dim blue and green Light intensity(80-120 lux),ovarian development and maturation or spawning of feamles occured respectively in 64.8% and 15.5% of test animals，with a total induced effect of 80.3 percent.The females showed their ovarian development in 10 days or longer after the induced treatment.Prawn's size and seawater temperature were closely related to gonadal develop-ment and spawning. Usually the females with a body weight over 70 gram in tha season of May to September with a higher water temperature (average T of 25.0-29.5℃)were more easily successful in inducement. Spawning behavior of females(11 times in total during experimental periady accured only in those months with higher water temperature.