Thermal structural optical integrated analysis is an effective way to estimate optical image quality during optical and mechanical design stage. Thermal structural optical integrated analysis of a small lens system is conducted. The results indicate that thermal aberrations of the system are higher, affecting optical properties of the system. Contribution to the thermal aberrations induced by change of refractive index is larger than that by surface deformation. Thermal conductance between the lens and the support structures, air turbulence in the upper and lower windows, and environmental convection of the outer surface of the mechanical structure influence the thermal aberrations finitely, and the primary influence factor is thermal load. Reducing thickness of the lens and absorption rate of materials will decrease thermal load and thermal aberrations of the system decreased effectively.