Abstract: In this paper, six kinds of garden tree were used to study the response mechanism to the biogas slurry irrigation by using pot control slurry irrigation method. The result showed that:(1)After slurry irrigation, the height of Hibiscus, Osmanthus, cherry, Ligustrum lucidum increased with the increase of biogas slurry concentration, while the height of Malus halliana increased only at T1 and T2 biogas slurry treatments and Viburnum awabuki at T1,T2,T3.(2)The pH of soil under all five slurry irrigation treatments reduced, but total nitrogen, available nitrogen, available phosphorus, available potassium, organic matter content of garden soil increased under all five slurry irrigation treatments, but these matters amount in soil of each tree species was different each other.(3)Available Zn content of soil increased firstly and then decreased with irrigation concentration increasing, its maximum value appeared at 6 L of biogas slurry treatment; the Fe content of soil increased with the irrigation concentration increasing. The experimental results indicated that biogas slurry application could improve soil fertility, but must be used rationally, otherwise which could impact on the growth of seedlings and could pollute the soil.