Generator of square waveform is important in designing, using and maintaining electrical equipment. The requirements of frequent precision and stabilization of the generator is increasing. Design of a generator based on the DDS and DSP chip is presented. In the design, DDS chip generates square waveform. DSP chip controls DDS chip to change the frequency and duty ratio. It is programmable and offers various communication interfaces. The design is adopted for the delay pulse generator of L625 lidar presently. It also can be useful for other equipments which need high-powered signal generator.