NOVELTY - Preparation of micron-sized spherical monocrystalline particle includes mixing elemental copper powder/copper sulfide (CuS) powder, elemental zinc powder/zinc sulfide (ZnS) powder, elemental tin powder/tin sulfide (SnS) powder and elemental sulfur powder or CuS powder, ZnS powder and SnS powder, adding fluxing agent to obtain copper-zinc-tin-sulfur nanoparticles, uniformly grinding, and mixing to obtain precursor; adding into quartz reaction vessel, and high temperature oxyhydrogen flame sealing; and heating, rapidly cooling, taking sample, washing, and drying.    USE - Method for preparation of micron-sized spherical monocrystalline particle used for solar energy battery (claimed).    ADVANTAGE - The monocrystalline particle has uniform size and better performance than prior art. The method has controllable temperature and recrystallization time.    DETAILED DESCRIPTION - Preparation of micron-sized spherical monocrystalline particle comprises:    (A) mixing elemental copper powder/copper sulfide (CuS) powder, elemental zinc powder/zinc sulfide (ZnS) powder, elemental tin powder/tin sulfide (SnS) powder and elemental sulfur powder or CuS powder, ZnS powder and SnS powder, adding fluxing agent to obtain copper-zinc-tin-sulfur nanoparticles, uniformly grinding, and mixing to obtain precursor;    (B) adding into quartz reaction vessel, and high temperature oxyhydrogen flame sealing under vacuum or inert gas condition; and    (C) heating to 750-1000 degrees C for 48-120 hours, rapidly cooling to room temperature, taking sample, washing, and drying.    The Cu/(Zn+Sn) has molar ratio of 0.76-0.95. The Zn/Sn has molar ratio of 1.1-1.2. The (Cu+Zn+Sn)/S has molar ratio of 1. The copper-zinc-tin-sulfur nanoparticles are prepared by dissolving zinc chloride, stannous chloride and cupric chloride at molar ratio of 1:1:2 in water, stirring to obtain clear solution; adding 0.1-0.3 M thiourea at volume ratio of 2.5-3.5:1.5-2.5, slowly stirring to obtain cloudy solution, and continuously stirring to obtain mixed solution; and placing into autoclave reactor, heating to 170-190 degrees C for 15-18 hours, cooling to room temperature, washing, centrifuging, and drying.