MgCl2 was used as the crystal surface regulator to regulate the selective growth of (001) crystal surface of MH by hydrothermal method, and the effects of concentration of crystal surface regulator, reaction temperature and reaction time on the dissolution and crystallization of MH particles were investigated. Compared with the raw material, the XRD peak intensity of the regulated products I001/I101 and I001/I110 increased by 214.30% and 307.45%, respectively, and that of the 100-ton pilot scale test products I001/I101 and I001/I110 increased by 84.08% and 112.99%, respectively. compared with the raw material. The morphology and structure of MH products were characterized by XRD, FE-SEM, TEM, FTIR, and particle size analyzer, and the regulation mechanism was investigated. The results show that MgCl2 can promote the (001) crystal face selective growth of MH in the hydrothermal system. On the one hand, MgCl2 as a strong acid and weak base salt lowers the pH of the system, while Cl－ can cause further accelerated dissolution of MH through charge neutralization effect. On the other hand, the Cl－ provided by MgCl2 acts on the crystallization process of MH and intensifies the growth of (001) crystalline facets by promoting the growth of MH edges. In this paper, we further investigated the effects of crystalline surface modifier concentration, reaction temperature and reaction time on the dissolution and crystallization of MH particles.