Abstract: To clarify the function of green manure crops in soil improvement and fertility increasing, the effects of different green manure crops ploughing back on the physical and chemical properties of tobacco planting soils were studied with a field experiment at fixed locations. The results showed that after green manure ploughing back for 3 consecutive years, soil bulk density reduced by 1.71%-23.87%, and the contents of organic matter, total N, total P, total K, alkaline hydrolytic N, available P, available K in soil increased by 3.73%-8.76%, 1.40%-3.50%, 31.37%-38.24%, 1.24%-5.15%, 1.50%-23.70%, 660.98%-833.72%, 335.83%-783.75%, respectively; the p H of soil did not change greatly in general. Gramineous green manure, especially Dongmu-70 Rye, affected soil bulk density and organic matter content obviously;leguminous green manure affected the contents of total N, total P, total K, alkaline hydrolytic N, available P, available K in soil obviously, notably Vicia villosa affected the contents of total Nand total P in soil and Milk vetch affected the contents of total K, alkaline hydrolytic N, available P and available K in soil more significantly.