In order to study the toxic effect of STX on mouse's blood with time lapse, STX from Aphanizomenon flosaquae was collected and the effect of toxins on physiological parameters of blood was measured by analyzing changes in cells and components in blood. Results showed that the blood parameters in mice changed after 0.5, 6, 12 and 24 hours respectively when mice were exposed to 0.5 Mu/ml Saxitoxin (STX). The numbers of red blood cell, Hemoglobin and platelet had little changed, while the number of white cells showed evident change, especially within 30 minutes. The more time extended, the less change of white cells had, namely, the effect of STX on some blood physiological parameters in mice became weaker with time spent. After 24 hours, almost all the blood physiological parameters in mice recovered to the normal level. Therefore, it can be concluded that both of STX and acid had toxic effects on blood of mice. When STX (0.5 Mu/ml, at pH5.3) were injected into blood, STX had the toxic effect within 12 hours, and after that, acid had.