Thermal decomposition of RDXCMDB propellants with burning rate catalysts (leadgallate，Cu(Ⅱ)paminobenzoic acid and carbon black) was investigated by using TGDSCFTIRMS simultaneous techniques. On the basis of changes in main gaseous products,the effect of the catalysts with various components on the characteristic values for TGDTG and DSC was discussed. Results show that the burning rate catalysts change the initial thermal decomposition mechanism of RDX. The C—N bond split which is in exothermic process has a predominance over competing branch reaction N—NO₂ bond split which is in endothermic process. The relative quantity of CH₂O (with negative heat of formation ΔH0f) produced from the decomposition of NC/NG component increases. The burning rate catalysts can make decomposition heats of the propellants increase and thus the burning rate rise. The compositions composed of nanosized lead saltcopper saltcarbon black have the best catalytic effect on RDXCMDB, and make the most obvious changes of the characteristic values and make the biggest enhancement of burning rate.