In this article, a eutectic mixture was prepared by mixing 1-methyl-3,4,5-trinitropyrazole (MTNP) and pentaerythritol tetranitrate (PETN) by a new method. The T-X phase diagram and H-X phase diagram were obtained by means of DSC analysis, and then the ratio of the eutectic was obtained. All systems displayed simple eutectic behavior. Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared (IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) were performed to characterize the structure of the eutectic. Thermodynamic analysis and TG-MS tests were carried out to explore the thermal decomposition of the eutectic. Then, the mechanical sensitivity and thermal sensitivity of the raw materials and the eutectic were tested, and the detonation performance was also calculated. The results show that the compatibility of the components of the eutectic is not perfect because of the intermolecular forces between the raw materials. Thermal the decomposition products are mainly H-2, H2O, N-2, CO, NO, N2O and CO2 and a small amount of CH4. The eutectic has the characteristics of high energy and insensitivity and is expected to replace TNT-based molten cast explosives.