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">Nano-sized Cu-Mg-Al hydrotalcite -like compound (HTLc) was prepared with low-supersaturation-coprecipitation method under invariable pH.The optimum reaction process conditions were obtained by single factor experiment,namely:the reaction happened in a ultrasonic wave reactor;invariable pH approached 7.5~9.0;n(Cu+Mg)/n(Al)=2.0~4.0;n(Cu)/n(Mg)=0.25~1.0;and freeze-drying method was adopted.Cu-Mg-Al-HTLc with single crystal phase was obtained under the above conditions and the product had a high degree of crystallinity and orderly crystal face growth.The product was also characterizatied by XRD</SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"; mso-bidi-font-family: "Times New Roman"; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">，</SPAN><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">FT-IR,and SEM.Results showed that most of the particles were nano-sized and the size was 50 nm. </SPAN>