By establishing a diffusion model, the solute distribution is investigated during the growth of eutectic phase from the binary melt on the primary phase. Based on the eutectic reaction conditions, reasonable assumptions are carried out to build the partial differential equation. After the determination of the initial and boundary conditions, the analytical solutions have been derived from the method of variables separation. The solute distribution ahead of interface and the influence of this distribution on the growth rate of heteroepitaxial phase are discussed.