Abstract: The zinc magnesium aluminum hydrotalcite-like compound Zn-Mg-Al-LDHs were synthesized by urea hydrother- mal method.The effects of many conditions，such as hydrothermal temperature，reaction time，the amount of urea，and the mix ratios，on the product were investigated，and the formation mechanism was also explored.Hydrotalcite samples were characterized by X-ray diffraction（XRD） and scan electron microscope（SEM）.Experiment results showed Zn-Mg-Al-LDHs with well-defined shape，obvious intercalated structure，uniform structure，and well-dispersing capability had been made when the preparation conditions were as follows：n（M2+）∶n（M3+）=2∶1，n（urea）∶［n（M2+）+n（M3+）］≥2，hydrothermal tempera- ture was 120 ℃，and reaction time was 48 h.The formation mechanism proposed for ZnMgAl-CO3 LDHs was the hydrolysis of urea，precipitation of zinc carbonate，precipitation of aluminum hydroxide，precipitation of zinc hydroxide and magnesium hydroxide，hydrolysis，precipitation nucleation，accumulation of hydrotalcite nano-pieces，crystal growth，and crystal formation. The characteristics of morphology transformation process included spherical particle，rosette，and six-party flake.

Key words: ZnMgAl-CO3 LDHs, synthesis, characterication, formation mechanism