As the excitation signal in the bioelectrical impedance measurement system, the constant current source needs to output a wide frequency band and stable current. In this paper, a program-controlled broadband constant current source design scheme is proposed: With STM32 as the control core, sinusoidal voltage signal with adjustable frequency is generated though the DDS. Tietze current pump a current conversion is performed with wide frequency bandwidth and small distortion. By the MCP41010 digital potentiometer, a numerical control gain amplifier circuit is designed to solve the problem of high frequency attenuation of constant current source. Based on the simulation experiment proved that the constant current source has excellent output characteristics with frequency and load changes, the constant current source transposition was developed. Experimental data shows that the controllable output frequency range is 0 ~ 1 MHz, the load capacity range is 0 ~ 5. 4 kΩ. The average error of the current effective value changes with frequency and load is 0. 137% and 0. 251% respectively. Proved that it has the characteristics of wide output frequency band, strong load capacity and stable current output which can meet the needs of bioelectrical impedance spectrum measurement.