This paper studies the influence of moisture content on the thermal stabilities of double-base propellant and multi-nitro ester propellant. The thermal behaviors and chemical kinetic parameters of the above two propellants and their mixtures with water were analyzed by using a CALVET heat flux calorimeter, C80. The thermal decomposition mechanisms of these two propellants with water were conjectured based on the tests. And then, the self-accelerating decomposition temperatures (SADT) of these two propellants and their mixtures with water were calculated and compared according to the kinetic parameters and Semenov model. The results show that the thermal decomposition mechanism of double-base propellant with water may be changing with the varying moisture content by transferring hydrogen proton (H(+)). However, the thermal decomposition mechanism of multi-nitro ester propellant with water may be unchanging due to the excess of formaldehyde (HCHO). Water plays the external physical factor on the thermal decomposition of multi-nitro ester propellant, and it plays both the physical and the chemical factors on the thermal decomposition of double-base propellant. The SADTs of their mixtures with water are much lower than that of pure propellants, and keep decreasing with the increasing of moisture content.