Abstract: The optimum formulation of 20% azadirachtin water dispersible granules was determined through the selection test of wetting agent,dispersing agent,disintegrating agent,emulsifier and sizing agent.40% Azadirachtin dry powder 50%,NekalBX 3% as wetting agent,NNO 5% as dispersing agent,ammonium sulfate 4% as disintegrating agent,0201B 5% as emulsifier,polyvinyl alcohol 0.1% as cohesion agent and silica as filler were formulated into an optimum formulation.Product properties and testing method were described.The granules had good dispersibility,and suspension rate was over 90%,wetting time was less than 20 s,dispersing time was less than 2 minutes,and decomposition rate was less than 5% after heat storage at (54±2)℃,14 d.All the specifications were up to grade.