Abstract: The trend of grain yield and the change of average yield per unit area and planting areas in Liaoning province in recent years was studied, and the stepwise regress analysis was applied to study the effect of grain yield per unit area and total planting area on total grain yield. The main results were as follows, the total cultivated area of Liaoning province has declining tendency in recent 26 years, the total grain yield and the grain yield per unit area increased in “wave” style; the grain yield per unit area and total planting area had the great effect on total grain yield, and the effect of yield per unit area on total grain yield is bigger than that of planting areas; the yield and the planting area of different crops also affected total grain yield greatly, and maize, rice, durra, wheat affect the total grain yield by grain yield per unit area , while millet, maize, wheat affect the total grain yield through planting area changing .