Seaweed macroalgae is one of marine natural product which shows a potent anticancer activity. In this work, we developed seaweed Eucheuma Sp. collected from east Lombok beach, Nusa Tenggara Barat, Indonesia, as potential anti-colorectal cancer agents. Seaweed macroalgae Eucheuma Sp. were extracted in four kind of organic solvents of hexane, ethylacetate, chloroform and ethanol, respectively. The extracts were tested for its phytochemical composition, and were then analyzed by Thin Layer Chromatography (TLC). Furthermore, anticancer activity of hexane, ethyl acetate, chloroform and ethanol extracts of Eucheuma Sp. were examined against colon HCT-116 cells by MTT cell proliferation assay. Phytochemical test of the extracts of Eucheuma Sp. showed positive result for metabolite of flavonoid, triterpenoid, alkaloid and tannin, whereas the TLC analysis revealed that the extracts containing five chemical compounds. Ethanol, hexane, chloroform, and ethyl acetate extracts of Eucheuma Sp. exhibited a good anticancer activity against colon HCT-116 cells with IC50 value ranging from 16.82 µg/mL to 40.45 µg/mL. The results suggest that seaweed Eucheuma Sp. could be further developed as a candidate for the new anti-colorectal cancer agents.