The invention discloses a fructus alpiniae oxyphyllae and compatible lindera aggregata extract for treating diabetes. The extract mainly comprises extract of petroleum ether part of fructus alpiniae oxyphyllae and compatible lindera aggregata extract, wherein the fructus alpiniae oxyphyllae and lindera aggregata are decocted with water according to the proportion of 1: 1 in a conventional way for three times, and concentrated solution is collected, so that dry extract can be obtained. The method comprises the steps of grinding, screening, carrying out reflux extraction, filtering, adding a solvent for extracting, recovering the solvent, carrying out ultrasonic extraction on lindera aggregata extract solution and preparing. According to the fructus alpiniae oxyphyllae and compatible lindera aggregata extract for treating the diabetes, and a preparation method of the extract provided by the invention, the harm of the diabetes to a patient is improved by the petroleum ether part of fructus alpiniae oxyphyllae extract, diabetic nephropathy (DN) can be treated by the extract, and kidney function decrease can be delayed; the fructus alpiniae oxyphyllae and compatible lindera aggregata extract is capable of promoting down regulation of the p27kip1 protein expression, has the functions of relieving kidney hypertrophia, reducing proteinuria and protecting the functions of the kidney, can effectively prevent diabetes complications, and is good in diabetes treatment effect.