The present invention discloses water suspended nano pesticide capsule preparation prepared via emulsion polymerization process. It has capsule shell of styrene, isocyanate, acrylate and methacrylate copolymer, and core comprising ididacloprid, high effect cypermethrin or diflubenzuron as effective component; contains pesticide 0.2-5 wt%, capsule shell 5-30 wt%, additive 10-35 wt% and water in proper proportion. The nano capsule is disersive spherical particle of size smaller than 100 nm. Compared with traditional pesticide preparation forms, the present invention has the features of water based solvent, nano level dispersive effective component, high stability, etc. and may be used in killing various pests of fruit tree, vegetable, flower, cotton, tobacco, etc.