We chose octyl-grafted alginate-amide as capsule material to prepare water suspension nanocapsule made of λ-cyhalothrin based on micro-emulsion template. The morphology of nanocapsules was characterized by transmission electron microscopy; the size of nanocapsules was characterized by laser particle size analysis and the effects of different octyl-grafted alginate-amide derivatives, calcium chloride and the amount of surfactant on the sizes of nanocapsules were discussed with the analysis of capsule particle sizes by laser particle size analyzer; moreover, the release performance of the nanocapsules was studied by the release quantity of λ-cyhalothrin determined by gas chromatography. The results indicated: the size of nanocapsules decreased with the increase of surfactant content; the average size of water suspension nanocapsules was 7.76nm when w (λ-cyhalothrin) =2.5%, w (surfactant) =17.5%, w (octyl-grafted alginate-amide derivative) = 1‰ and w (calcium chloride) = 0.5‰; in order to obtain 60% of release rate of chlorine fluorine cyanide chrysanthemum ester with high performance, the micro-emulsion needed 200min and the nanocapsule needed 300min. In all, the nanocapsules restrained the release of core drug.