A method of a cuprous chloride crystal growth is disclosed, which belongs to the intraocular lens and the crystal growth field of the optoelectronic functional materials technology field, especially relates to a photoelectric crystal material. The method comprises the following steps that: an ionic liquid which contains brine ions is used as a growth solvent; a cooling method is used to achieve crystal growths. Equipments for growing crystals are simple and the technology is easy to be controlled. Through using the method, crystalline forms are complete; grown crystals have fewer defects and large sizes. The grown crystals have important application value in aspects of Q-switched laser, photoelectronic technique and the like.