The cyclotetramethylene tetranitramine (HMX)/ammonium perchlorate (AP)/energetic polymer (EP) nanocomposite was prepared by a co-precipitation method using a novel EP as matrix. Its structure and properties were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), specific surface area (Brunauer-Emmett-Teller (BET)) measurement, Infrared (IR) spectrometry, and differential scanning calorimetry (DSC). Results show that the HMX/AP/EP nanocomposite possesses the three-dimensional nano-network structure. The HMX and AP particles are uniformly deposited on EP, whose size is in the range of 50-200 nm. HMX, AP and EP are closely bonded each other with good compatibility. The thermal decomposition temperature of the HMX/AP/EP nanocomposite is far lower than that of HMX. When the oxygen balance of HMX/AP/EP nanocomposite is zero, its decomposition heat is up to 2570 J·g^-1.Compared with the characteristic drop height of impact sensitivity (H₅₀) of 27 cm of HMX, the value of H₅₀ of the HMX/AP/EP nanocomposite is 50.49 cm, revealing that the latter has lower mechanical sensitivity.