The present invention discloses a preparation method of a sulfur coated urea for rice. According to the preparation method, large particle urea passes through flowing melting sulfur to achieve urea coating; then melting paraffin wax is sprayed, and cooling is performed to a room temperature; after cooling, a conditioning agent is added to the sulfur coated urea, wherein the conditioning agent is dolomite powder or diatomite, and is adsorbed on the surface of the sulfur coated urea particles, an absorption amount is 1.2-3% of the weight of the sulfur coated urea, and addition of the conditioning agent is performed inside a roller sieve; after mixing screening, the resulting material on the sieve is the finished product. The sulfur coated urea prepared by the method of the present invention has the following characteristics that: a surface structure of the sulfur coated urea particles is changed, diffusion speed of water on the surface of the sulfur coated urea particles is increased so as to rapidly sink in the water, a floatation problem of the existing sulfur coated urea is effectively solved, a fertilizer application is improved, production cost is relatively low, and product quality is not affected.