In view of the problems in the brushless DC motor drive system, such as the difficulty of analog PWM technology control, the lack of PWM chips and the low precision of PWM dead time, this paper designs a pure digital PWM waveform generator using Verilog language. This paper briefly introduces the control principle of PWM in brushless DC motor system, the relationship between motor rotor position and motor phase conduction and the PWM modulation mode, and emphatically describes the design process of PWM waveform generator using pure digital method. By adding a clock divider module, the clock frequency of dead-time counter can be increased to 16 times that of PWM counter. Two channels of PWM share a dead-time counter, saving design resources. The designed PWM waveform generator can be configured through SPI interface to realize the advantages of programmable, convenient control and so on.