Antiparasitic activity of the microalgae Cladophora crispata isolated from Garmat-Ali River in southern Iraq was studied. Water samples were collected from river in the northern of Basrah, and cultured in chu-10 medium. Supernatants, alkaloidic and ethylacecate extracts from biomass were extracted and screened against the hydatidosis compared with albendazole drug. The present study reveal that 2-(N, N-dimethyl hydrazine) cyclohexanecarbointrile and pyridine 2, 3, 4, 5-tetrahyro compounds have activity against the protoscolices of hydatid cysts accordingly to the activity of albendazole based on the mean of weight of mice, mean of hydatid cysts number, mean of diameters and weights of hydatid cysts. The current study concludes that the alkaloidal and ethylacetate extracts of Cladophora crispata have a positive effect on the protoscolices of hydatid cyst in comparison with albendazole activity, related to reduction in the number and weight of hydatid cyst as well as the obstruction of germinated layer which is responsible for proliferation of protoscolices.