A baseband circuit for wireless speech acquisition Transmitter is presented, including speech coding circuit based on G.726 algorithm and high energy-efficient communication control circuit. The communication circuit uses self-defined communication protocol, which can implement modulation and transmission functions. Some optimizations such as hardware reuse, CSD coding and duty cycle control technology are used to reduce the size and power consumption in ASIC design. The speech coding circuit is verified by PESQ algorithm. Simulation results show that the quality of output signal can meet application requirements. It can achieve a MOS of 4.0. The baseband circuit is realized in UMC 0.18μm CMOS process. The circuit area is 0.66 mm2 and the power consumption is 0.58 mW.