The optic switch can output the single laser beam output by the fiber laser through multiple channels to realize the "one device and multiple applications" of the laser. It is the key device of modern laser intelligent manufacturing. As the power of the optic switch is up to 10 kW level, thermal effects happen easily in the coupling system, which affects the performance of the optic switch. In order to solve the problem of effective control of thermal effects, ensure the efficient coupling and high-quality output of the 10 kW-level optic switch, the physical mechanism of thermal effects in the coupling system was studied by finite element analysis. And a novel method based on water circulation and flow around cooling was proposed to control the thermal effects of the system. Through the verification of serial 10 kW-level experiments, it indicated that under the guarantee of the method proposed in this paper, the high-power optic switch was able to carry 10 kW-level power for a long time. The coupling efficiency was maintained above 98%. The thermal aberration of the system was suppressed, and the stability of the beam quality of the laser output by the optic switch can be guaranteed. This study provides an effective means for the analysis and treatment of thermal effects in the high-power laser system.