Cystic Echinococcosis is an important zoonosis in the sheep rising areas of Iran. To develop a simple and reliable diagnostic method for Echinococcus infection in definitive hosts, E. granulosus polyoclonal antibodies (PolyAbs) were prepared from adult worm in rabbit. A selected PoAb was used for coproantigen detection in faecal samples obtained from animals naturally infected with Echinococcus and compared with necropsy method. Finally, the sensitivity and specificity of the test were evaluated. The results indicated E. granulosus worms was detected in 36 (43%) of small intestine contents of dogs. The results obtained by CpAg- ELISA test showed 30 (36.14%) positive and 53 (63.86%) negative cases. The sensitivity and specificity of CpAg-ELISA test were evaluated 83.33% and 100% respectively. In conclusion, the present result suggests that, CpAg-ELISA is a valid test for detection of E. granulosus infection in living dogs. Thus it is appropriate to apply for epidemiological study.