In this paper the procedure for the study of anticancer drug screenning on colon cancer cell line SW-480 using MTT （tetrazolium dye） assay has been observed in vitro. Our study showed that（l） The optimal target cell concentration was 1-5×10

4

cell/well. （2） The optimal MTT concentration is 5 mgml

-1

when a range of 0-10 mgml

-1

was tested. In view of the relatively small increase in sensitivity obtained after 6h

we chose 4h incubation as optiomal incubation time. （3） DMSO and acid isopropyl alcohol were both effective to dissolve the formazan produced but greater solubility and absorbance reading were seen using DMSO. （4） The addition of new born calf serum to the reaction mixture results in a gradual lowering of optical density than that produced by serum-free medium before the addition of DMSO.The assay is simple and rapid with a CV within groups about 10%. when using DMSO as a solvent in this assay

it is necessary to read the plates within 30 mim after adding DMSO. Meanwhile

the chemosensitivity of SW-480 cell to 72h exposrre to four kinds of standard anticancer drugs was different.