To explore the effects of ploughing depth on root growth and soil enzyme activity of potato in north foot of Yinshan mountain，the effects of four different ploughing depths of 20 cm (D20，CK)，30 cm (D30)，40 cm (D40)and 50 cm(D50)on dry matter accumulation，activity of root of potato and soil enzyme activities，including catalase，alkaline phosphate，urease and sucrose，were analyzed. The results showed that the deep ploughing of D40 and D50 treatment，compared to D20 and D30 treatment，improved root activity significantly and enhanced root dry matter accumulation in starch accumulation stage，increased by 75.2%-292.1% and 23.4%-30.2%，respectively. Through the soil enzymes activity analysis，deep ploughing (D30，D40，D50 treatment)had little effect on the activities of catalase and sucrase in potato fields，but had a great effect on alkaline phosphatase and urease activities. Deep ploughing improved soil alkaline phosphate activity in soil layers of 0-20 cm in whole growing period and 20-60 cm in seeding stage. Among them，D40 and D50 treatment increased remarkably in soil layers of 0-20 cm from tuber expansion period to the starch accumulation stage and 40-60 cm in seeding stage. Deep ploughing D30，D40 and D50 treatments significantly increased the urease activity in 0-20 cm soil layers in the whole growth period，from tuber expansion stage to starch accumulation period，and starch accumulation period，respectively. Meanwhile，they improved the urease activity in 20-60 cm soil，among which the urease activity of D40 and D50 treatment increased significantly by 33.8%-80.0%. In conclusion，the ploughing depth of 30 cm was still the stress depth for potato root growth，and the deep ploughing of 40 cm had the best effect on promoting potato root growth and increasing the activities of alkaline phosphatase and urease in potato field.