The gain characteristics of the optically pumped vertical external cavity surface emitting lasers is introduced in detail. To take the InGaAs/AlGaAs strained quantum wells as an example, a complete system model is established which considers all the effects of the band-edge offset, band structure and gain material. The Model-Solid model is used to determine the band-edge-offset ratios, and then the parabolic approximation of conduction band and the 6×6 Luttinger Hamiltonian of valence band are used to calculate the energy-band structure and material gain. Based on the analysis of the characteristics of material gain, the active region of a 1 μm wavelength band quantum well is optimized, and the quantum well width, well depth, and configuration of the well are respectively optimized, then the optimum selections of which are obtained. The calculated results provide a theoretical basis for optimized designing of optically pumped vertical external cavity surface emitting lasers.