The mass of wheat sample and the volume of alcohol are key parameters in specific gravity test of wheat. The effect of sample mass and volume of alcohol on the specific gravity of wheat are studied with wheat samples from five regions in China. The results showed that the gravity increased gradually along with the increase of the mass of wheat samples, until to a steady value finally; while the volume of alcohol has little effect on the specific gravity of wheat. The measured value of wheat sample mass in existent specific gravity experiment standard is smaller than that obtained in this study cause the measured specific gravity lower than actual. The contrast test showed that the mass of wheat sample should not less than 100 g in the specific gravity test, which is far more than 10 g recommended in the current standard.