Abstract: Objective To study the field effects and effective duration of cypermethr in congfected by chitosan against fly and mosquito.Methods After all preparations were applied to experimental field,the density's changes of fly and mosquito were observed periodically,and relative population index and mortality rate were used to eveluate the effects.Results The cypermethr in prepar ation could control pests for 2 months,but the effective duration of cyper methrin confected by chitosan was more than 3 months.Conclusion The study proved that chitosan could control the release of cypermethrin.