Abstract: In this article, MTT assay is adopted to study three different kinds of ethoxylate fatty alcohol on Chinese Hamster Ovary（CHO）cells and Hela cells. The results indicate that the reproduction restraining effect of fatty alcohol ethoxylates both on CHO cells and Hela cells gradually decreased as the numbers of EO increased. In the other words, AEO5 shows the maximum inhibitory rates, followed is AEO9, and the minimum is AEO15. When the concentration of AEO5 is more than 0.05μL/mL and AEO9 is more than 0.075μL/mL, both their trend toward gentle inclined. When the concentration of AEO15 is 0. 1μL/mL, it’s growth inhibition rate still shows upward tendency. When the concentration of AEO5 and AEO9 are less than 0.005μL/mL, their reproduction restraining effects on CHO cells and Hela cells are unconspicuous. When the concentration of AEO15 is no more than 0.01μL/mL, its reproduction restraining effect on CHO cells and Hela cells is obsolete.