Cancer is deliberate to be caused by the interaction between genetic susceptibility and environmental toxins. Based on the DNA changes in cells, proliferating cycle of tumor cells can be divided into 4 phase’s Pre-synthetic phase (Gap 1 phase or G1 phase). The antiproliferative activities of these compounds were evaluated against a Cytotoxicity analysis of compounds against leukemia cell line -K562 organism homo sapiens (human) organ bone - marrow.Tissue - lymphoblast, disease - chronic myelogenous leukemia (CML) one human tumor cell lines (K562) by applying the MTT colorimetric assay. The 1, 3-disubstituted urea derivatives show good antiproliferative activity against human cancer cell lines (K562). Generally, an aromatic ring on N-3 seems to be in favor of enhancing the inhibitory activity, compounds introduced a Nitro group substituted at C-3 position on the aromatic ring approved to generally decrease    activity. Cells were incubated with different concentrations of the extract for 5 days in a 96 well plate, after which the liver cells which did not take in stain and dead cells which took in stain were counted. For counting the cell suspension was mixed with an equal volume of trypan blue and was counted. A concentration that inhibited the growth of cells at 50% (IC50) was computed. Substances with low IC50 indicate potential for cytotoxicity. (A) 1, 1-dimethyl-3-phenyl-3-(5-phenyl-1, 3, 4-thiadiazol-2-yl) urea was found higher activity