The advantage of the Grey Model is that it can obtain a good forecasting effect as long as a little historical data are provided. The simple Grey Model GM(1,1) can forecast changeable trends; however, it may produce serious errors at the turning points in a curve. Hence, the aim of this research is to discover a solution to improve the condition just descrived. First, the factors which cause the turning points can be analyzed and digitalized as influential weights. In addition, the usage of these factors can also make the historical data smoother. Through a forecast from GM(1,1), these factors still need to be added to the GM(1,1) Model forecasting values at the next time point so that the forecasting values can be produced there. Meanwhile, deviation in any forecast cannot be avoided; hence; this research also uses the Auto-regression Model to forecast deviation and modify it from the forecasting values. Actual data can be used to verify the research. The accuracy of the GM(1,1) Model is indeed increased by a combination of an improved GM(1,1) Model and deviation modification. The examples in this research are verified to be, indeed, better than the traditional forecasting models.