Abstract: ObjectiveThe aim of the present study was to evaluate the acute toxicity of mesotrione in different for-mulations and technical materials to zebrafish,provide basic data for environmental ecological risk assessment for mesot-rione. At the same time,it could provide reference for rational use of this pesticide.MethodAcute toxicity of mesotrione in different formulations and technical materials to zebrafish was evaluated using static test. Toxicity levels of median lethal concentrationto zebrafish in 96 h(96 h-LC50)for the tested pesticides were divided based on Experimental Guideline for Environmental Safety Evaluation of Chemical Pesticides(GB/T 31270.12-2014).ResultUnder the same exposure time,LC50 of mesotrione in different formulations and technical materials to zebrafish was different. 96 h-LC50(95%confi-dence limit)of 10%mesotrione oil dispersion(OD)was the lowest6.70(5.18~8.15)mg a.i./L,followed by 10%mesot-rione suspension concentrate(SC),and 75%mesotrione water dispersible granule(WDG)which were 10.89(9.29-12.43) and 38.97(30.83-47.51)mg a.i./L respectively. 96 h-LC50 of 98%mesotrione technical material(TM)to zebrafish was the largest,more than 1.00 × 102 mg a. i./L. According to the Experimental Guideline for Environmental Safety Evaluation of Chemical Pesticides(GB/T 31270.12-2014),the toxicity of 10% mesotrione SC to zebrafish was moderate,while the others were low. The rank of toxicity was:10% mesotrione SC>10% mesotrione OD>75% mesotrione WDG>98%mesotrione TM.ConclusionAcute toxicity of mesotrione in different formulations and technical materials to zebrafish is different,the rank is as follows:mesotrione SC>mesotrione OD>mesotrione WDG>mesotrione TM. Therefore,in field cultivation,the formulations of pesticide should be selected accordingly,and the application dosage should be controlled to reduce the negative influence on fish caused by pesticides entering water area environment.