Abstract: <SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-bidi-font-size: 12.0pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体">Crystal size is the most concerned quality index of sodium chlorate users.Whole process of vacuum crystallization of sodium chlorate was introduced.Mechanism of vacuum crystallization process of sodium chlorate as well as the factors influencing crystal nucleation rate and crystal growth rate in production process was specially studied.Influences of crystallization interval,external circulation rate,crystal seed,and small cycle mode on crystal nucleation rate as well as influences of liquid level in crystallizer,density of liquid,and temperature on crystal growth rate and growth time were presented in detail.Concrete operation plan for producing sodium chlorate with larger and more even size was obtained. </SPAN>