In order to improve the safety performance of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), nano CL-20/AP（ammonium perchlorate) energetic composite particles were readily prepared via a one-step ball milling method, a facile, clean, and continuous synthesized strategy. The prepared samples were studied by scanning electron microscopy(SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and impact sensitivity test. The SEM results show that the CL-20/AP composite particles are smooth on surface and nearly spherical with size of 300-500 nm. The XRD peak position of CL-20/AP is obviously deviated and some peaks are even disappeared, which means new crystalline phase may be formed. Due to the preferred orientation of the polycrystalline samples, the XRD peak intensity is reduced. The thermal decomposition peak of CL-20/AP decreases. The impact sensitivity result shows that the H₅₀ of the nano CL-20/AP composite particles is 26.07 cm, which increases by 13.10 cm compared with raw CL-20, indicating a better safety performance.