NOVELTY - Method of using urban sewage treatment plant sludge as forest soil substrate involves planting the soil, for ensuring logging in to outlet, land to irrigation; planting ground block by selecting sludge composting field of compost field; adding sludge and slag additive to the sludge compost field; and fermenting the compost product after used for forestry administration.    USE - For using urban sewage treatment plant sludge as forest soil substrate (claimed).    ADVANTAGE - The method provides environment protection; solves the problem of sludge compost treatment; and realizes the recycling use of resource; shortens the growth cycle of the wood; avoids the use of harmful substance in the sludge; and does not show toxic symptoms.    DETAILED DESCRIPTION - Method of using urban sewage treatment plant sludge as forest soil substrate involves planting the soil, for ensuring logging in to outlet, land to irrigation; planting ground block by selecting sludge composting field of compost field around digging ditch that is set above the plastic film of the greenhouse, where the sludge compost field is for tamping, then paving waterproof coiled material containing certain gradient, and percolate trapping barrel, where the outer side id provided with a condensed water guide groove; adding the sludge and slag additive to the sludge compost field, mixing them according to weight ratio of 1.5:1, where the sludge is 75-85%, and the slag additive is 25-35%, and then adding proper amount of inoculating and fermenting composite microbial inoculum for 1-20 days, where the inoculum is fed once every 2 days to turning the compost sludge once, for the purpose of oxygen, or 20-32 days, where the inoculum is fed once every 4 days to turning the compost sludge to control the temperature as main purpose when the composting sludge is 25-35%, where the carbon to nitrogen ratio in the forest soil matrix is 20:1, and where the oxygen consumption rate is stable, and fermenting the compost product after used for forestry administration, using, turning the soil ridge or furrow applying, when used for green direct administration, firstly before the plant above the soil uniformly spraying sludge, and then combined with soil to turning the soil, the sludge and soil uniformly, after turning the soil is sludge, a small amount of water to soil and mud.