In this paper, the theoretical modeling of intra-cavity pumped laser used to simultaneously output quasi-three-level laser and four-level laser is proposed. Due to the two laser generating in different gain medium, the gain competition can be avoided. In the modeling, the plane wave approximation is employed, and the analytical expressions of the output power of dual-wavelength lasers are derived. The output characteristics are obtained by numerically simulating, and the impact of changing some critical parameters on the output characteristics are investigated. It is found that by increasing the absorption coefficient of the second gain medium at quasi-three-level radiation, or reducing the output mirror transmittance of the laser, the output power of four-level laser will be promoted, while the output power of quasi-three-level radiation will be turned lower. [ABSTRACT FROM AUTHOR]