CsPbBr3Cs4PbBr6 perovskite composite nanocrystals (NCs) were successfully prepared by mechanochemistry method at room temperature, introducing trace amounts of methanol and oleylamine as ligands. The nanocrystals were tested by powder Xray diffraction (XRD), elemental content analysis (EDS), ultravioletvisible spectroscopy (UVVis), photoluminescence(PL) spectroscopy and transmission electron microscopy (TEM). Compared with the samples without methanol, the luminescence intensity of the samples with 0.85 mL methanol increases by 58%, and the quantum yield (PLQY) increases from 11% to 55%. Moreover, the presence of Cs4PbBr6 in the composite NCs improves the stability of the samples at room temperature. This experiment confirm that the introduction of methanol in the mechanochemistry preparation process could adjust the composition of the complex nanocrystals, thus significantly improving the luminescence intensity and stability of the products, which provides a new idea for the synthesis of luminescent nanocrystals at room temperature.