The thermal decompositions of RDX-CMDB modified double base propellants with a composite burning catalyst were investigated by using of PDSC and TG-DTG. It is shown that the influence of the burning catalysts with different components on the characteristic values of PDSC is different in the decompositions of RDX-CMDB, Which is similar to the catalyst on burning rate. The characteristic values, which are the square roots of heat release rate and pressures on PDSC tests, can be correlated to burning rates of RDX-CMDB by using a liner equation. The k_u, correlation factor of burning rate with PDSC characteristic value, can be used to study the effect of burning catalysts on burning rate of the propellants.