Abstract: An acute toxicity test of ricin on loach red cells was conducted by applying solutions of different ricin concentrations at 0.02, 0.04, 0.06, 0.08 and 0.10 g/L. On the 1^st, 3^rd, 7^th and, 11^th days, the loach tails were cut off and blood smears were made to find about the red cell apoptosis. The findings showed that: the apoptosis of ricin on erythrocytes of loach was marked by an obvious time and concentration dependency. At the early stage of the toxicity test, the red cell apoptosis rate increased as the ricin concentration ascended; yet with the extension of exposure time, the apoptosis rate curve reached its peak value, then the apoptosis rate decreased persistently with the overall apoptosis curve taking the shape of a parabola.. Conclusion: ricin can induce apoptosis in erythrocytes of loach