Abstract: In this paper, the system of Anopheles stephensi and Plasmodium yoelii yoelii was used as animal model. The soluble protein and esterasc isozymes of adult female mosr quitoes at various times after taking noninfected and plasmodia-infected blood meal were investigated.The result shows that the amount of soluble protein in plasmodia-infected mosquitoes was lower than that in noninfected ones (P0.01); the activity and electrophoretic patterns of EST in infected mosquitoes being also different from those of the noninfected ones.