In order to study the effect of fuel Mg and metal oxide CuO on the reaction of thermite, different proportions of Al-Mg alloys and MoO3-CuO metal oxides were prepared by mechanical ball milling, and then the samples of Al1-xMgx/(MoO3)(1-x)CuOx composite thermite were prepared by ultrasonic dispersion method. The samples were characterized by SEM, TG-DSC, and constant pressure combustion experiments. The results show that in quaternary thermite, adding CuO increases initial exothermic temperature, but increases exothermic heat in high-temperature regions, and effectively reduces the activation energy of the thermite reaction. On the contrary, adding Mg reduces exothermic heat in the high-temperature areas, but reduces initial exothermic temperature. After calculation, the quaternary thermite with the best exothermic performance is Al0.8Mg0.2/(MoO3)(0.5)CuO0.5. Its initial reaction temperature is only 614 degrees C, but the heat release is up to 2217 J/g. Its activation energy is only 106.7 kJ/mol, but the critical temperature of thermal explosion is up to 927.9 K. At the same time, Al0.8Mg0.2/(MoO3)(0.5)CuO0.5 has better combustion performance. During combustion, the flame is jet-like, and the main products are Al2O3, Mo and Cu. This work provides a reference for studying the thermal safety and combustion performance of quaternary thermite.