Hydromagnesite with different morphologies has been synthesized using magnesite as raw materials. The influences of pyrolysis temperature, the pH value of the magnesium bicarbonate solution and pyrolysis time on the preparation process of hydromagnesite were investigated. The synthesized samples were characterized by Xray diffraction (XRD), scanning electron microscopy (SEM) and fully automatic specific surface meter (BET). The phase transition process and mechanism of hydrated magnesium carbonate with different crystal structures were further explored. The results showed that porous rod-like, porous flower-like and lamellar hydromagnesite was prepared at above 70 degrees C, 90min and different pH values. The specific surface area of porous rod-like, porous follower-like and lamellar hydromagnesite is 59.292m(2)/g, 34.568m(2)/g and 27.973m(2)/g, respectively. While the average pore sizes of the corresponding hydromagnesite are 15.172 nm, 15.368 nm and 17.132 nm, respectively. Based on the crystal assembly method, the structural stability of hydromagnesite is the highest compared with lansfordite and nesquehonite. (C) 2020 Published by Elsevier B.V.