The present paper is to study and build the rapid nondestructive prediction technique of wheat grain quality in the pre-harvest period, The analysis of SPAD value aimed at five different periods from the first leaf to the 4th leaf to obtain SPAD values with the sampling period and the changes of leaf using 31 kinds of wheat materials, near infrared spectroscopy was used for the determination of protein of the grain. And the leaf SPAD values and maturity correlation of grain protein content were established. It was found that decreasing rate of the top leaf SPAD and grain protein content showed significant negative correlation y=-3.210 9x+14.286, linear regression equation is y=-3.210 9x+14.286, and correlation coefficient is r=-0.849 0. With significant analysis, we assume that there is a very significant linear correlation between decreasing rate of the top leaf SPAD value and grain protein content. So we can use decreasing rate of the top leaf SPAD values to predict the protein content of grain.