The invention discloses a styrene-acrylic resin for toner and a preparation method thereof. The styrene-acrylic resin for toner is prepared from a hard monomer, a soft monomer, a functional monomer, a chain transfer agent, an emulsifier, an initiator, a pH regulator and water. The preparation method comprises the steps of: 1) preparation of a seed pre-emulsion; 2) preparation of a pre-emulsion; 3) preparation of a seed emulsion; 4) preparation of a styrene-acrylic emulsion; and 5) demulsification and spray drying of the styrene-acrylic emulsion, thus obtaining the styrene-acrylic resin for toner. The preparation method provided by the invention has the advantages of simple preparation process, short reaction period, mild reaction conditions, no need of special instrument and equipment, and the reaction medium is water, which has small odor, and is economical and environment-friendly. The styrene-acrylic resin for toner provided by the invention can achieve regulation of molecular weight, glass transition temperature, softening point and other properties according to actual needs, has low water absorption, good thermal stability and excellent performance, and is economical and practical.