In order to obtain a high-frequency tunable microwave signal source,a high precision thermoelectric cooler (TEC) temperature-controlled circuit is designe d by using a microcontroller in this paper.A digital temperature sensor of TMP112is used to collect temperature information,and TEC chip is drived by the generated pulse width modulation (PWM) from the control circuit.A single frequency Brillouin fiber laser is designed without using expensive instr uments or complicated system.The temperature of the Brillouin gain fiber in this laser ha s been controlled by the obtained controller,and the tunable microwave signal from 10.837GHz to 11.076GHz can be obtained through adjusting the temperature of the fiber and the pump wavelength. The generated signal frequency range can be further expanded and a microwave signal with the d esired frequency can be generated through this scheme.