The invention discloses a preparation method of environment-friendly PUR (polyurethane resin) compounded polyurethane synthetic leather. The method comprises the following steps: coating release paperwith a layer of thermosetting polyether type water-based polyurethane paste, and performing drying to form a water-based surface layer; then coating the water-based surface layer with a layer of polyether type solvent-free foam polyurethane paste, and performing drying to obtain a foam layer in a semi-dry state; attaching the foam layer in the semi-dry state to a base fabric, and after high-temperature aging, stripping the release layer away to obtain a compound layer; compounding the base fabric of the compound layer and single-sided napped fabric base on high-temperature thermal transfer compounding equipment by virtue of a PRU compound adhesive, and performing moisture curing to obtain a semi-finished product; tanning the semi-finished product to obtain the environment-friendly PUR compounded polyurethane synthetic leather by virtue of high and low temperature alternate continuous graining process of a continuous graining machine. The prepared synthetic leather has the characteristics of full pattern, strong granular sensation, high drape factor, soft and full hand-feel, strong leather pleating sensation, no solvent, total environment friendliness and resistance to scratch, wear and hydrolysis.