The invention relates to a series of novel-structure C12 sterides and glycoside compounds of C12 sterides in Cortex Lycii, a preparation method of C12 sterides and the compounds, and application of the compounds in preparation of drugs for treating/preventing diabetes. Pharmacological tests prove that in palmitic acid induced MIN6 cell injuring model, the C12 sterides and the glycoside compounds of the C12 sterides can effectively promote islet cell proliferation and can be used for preparing the drugs for blood glucose reducing.