Abstract: The inhibition effects of vanadium substituted  Dawson- and Keggin-type heteropoly acids(W,  P) on the polymerization  of  methyl methacrylate(MMA) were investigated by differential scanning calorimetry(DSC).  The results show that in terms of the same heteropoly acid, the rate of polymerization of MMA decreases continuously and the inhibition effect of heteropoly acid is better with increasing the amount of heteropoly acid; in terms of the different heteropoly acid, the rate of polymerization of MMA decreases continuously with the increasing of Vanadium atom number, that is to say, the more containing Vanadium atom, the better inhibition effect of heteropoly acid. On the whole,  the inhibition effects of  Dawson-type heteropoly acid are better than  Keggin-type heteropoly acid.