The invention relates to a velvet finishing agent for synthetic leather and a preparation method thereof. The velvet finishing agent consists of the following raw materials in parts by weight: 80-120 parts of polyurethane resin, 3-10 parts of dry smooth wax powder, 2-8 parts of silicon dioxide extinction powder, 6-15 parts of glass microspheres with particle size of 5-60 microns, 1-6 parts of epoxidized soybean oil, 1-6 parts of phenmethyl silicon oil, 1-6 parts of plasticizer, 30-60 parts of dimethylformamide, 30-50 parts of butyl acetate, 20-40 parts of methylal and 20-40 parts of dimethylbenzene. The velvet finishing agent for synthetic leather provided by the invention has low cost and good velvet feel, can be used through multiple technologies such as roller painting, printing and the like, and is widely applicable. In the invention, a preparation technology of uniformly dispersing before grinding and filtering is adopted, and the prepared finishing agent can obtain more delicate velvet feel; and moreover, as the yangbuck powder requiring accurate temperature control and long-time foaming is not used, the preparation is easier.