For the problem that energy conversion efficiency and lifespan of concentrated photovoltaic solar cells are greatly influenced by temperature, a method of monitoring and controlling the temperature of the concentrated photovoltaic power system based on the GaAs semiconductor absorption optical fiber temperature sensor is proposed. The results of numerical simulation experiment show that when the flow rate of the cooling water is reduced, higher temperature of the concentrated photovoltaic cells could be detected by the optical fiber temperature detection system. Then we can reduce the temperature of the concentrated photovoltaic cells through improving the flow rate of the cooling water. With prolonging the life of concentrator photovoltaic cells and improving the utilization rate of solar energy, the proposed method has a certain theoretical significance.