Abstract: In many selection theories and methods on agricultural machinery there was an significant flaw: neglect of intact rate of agricultural machinery. Intact rate of agricultural machinery indicates fine degree of agricultural machinery, which is an important factor in selection and optimization of agricultural machinery. It is not economical under too high or low intact rate conditions. So it is necessary to select and optimize the machinery under suitable intact rate. According to fiveyear data of tractor intact rate from 1991 to 1995 in Dongxin State Farm, a grey model GM(1,1) is established by grey theory. The forecasting results show the model is of very high accuracy, its deviation rate less than 1%. It can be applied to forecast intact rate of some year.