Cancer is the very dangerous cause of death in the world. Day by day the scientists are struggling to get a permanent solution. The soursop (Annona muricata) is a medicinal plant which is used traditionally as antitumor agent. The cytotoxic effects from extracts of leaves of soursop in cancer cells L929 fibroblast, HCT colon cancer cells, MCF7, HeLa, SIHA cell lines were done under this study. The extraction was carried out by microwave assisted extraction method using ethanol and fractionation by column chromatography. The various solvents were Petroleum ether, Petroleum ether: chloroform (4:3, 3:2, 2:3 and 1:4), Chloroform, Chloroform: Ethanol (4:3, 3:2, 2:3 and 1:4). Such ten fractions were collected. Cytotoxic test was done by the method of MTT assay by using the extract at different concentrations and the IC50 value was calculated ie values that produce inhibitory concentrations of cancer cells by 50%. At 50µg/ml the same assay was repeated by using ten different fractions. The results showed that the ethanolic extracts of leaves of soursop has a cytotoxic activity against L929 cell lines, HCT colon cell lines, MCF 7, SIHA and HeLa with IC50 values of 68.5, 187.5, 112.6, 23.4 and 24.9 μg/ml respectively. Among the ten different fractions at 50µg/ml, the fraction AM3 was showed best cytotoxic activity. In case of AM3, IC50 value was found to be 16μg / ml. The fraction AM3 can be selected for further study.