Chick embryos inoculated with sporozoites of E. tenella were used as a model for testing the activity of Bt crystal proteins. Each embryo were inoculated by a dose of 10000 pure sporozoites was injected with testing Bt crystal proteins before 24 hours. The varying oocyst inhibition rates of embryos brought about by Bt crystal proteins that were given at various doses were used as a criterion for determining the activity of Bt crystal proteins. The results demonstrated that BT6 was the most effective isolate among the 15 strains. According to the experimental results mentioned above, we believe that the use of chicken embryo infection with E. tenella sporozites for the determination of the activity of Bt crystal proteins is an efficacious method, which offers some advantages, such as simplicity of operation, good accuracy and only small requirement of expenses.