On the basis of the analysis of the AD9910，the Paper design a circuit for Frequency-shift keying (FSK) modulation. This circuit is controlled by a single-chip microprocessor MSP430F149, and can be used to generate a controllable FSK modulation signal. It can flexibly change the frequency of signal by programming the Micro Control Unit (MCU). This paper introduced the FSK modulation hardware circuit and software realization in this way. The signal is viewed by Oscillograph. Experiments show that this design is simple and highly applicable.