Abstract: This paper presented a 128-channel ultrasonic phased array transmitting system based on CPLD and high-voltage digital pulser.The system consisted of a module of controlling transmitting timing sequence, a module of driving transmitting timing sequence and a module of transmitting high-voltage, which possessed the features of high pulse-delay resolution and convenient modification of delay, width and polarity of pulse, and exhibited simple structure, low cost, high precision and reliability.After illustrating the principle of phased array transmitting, this paper described the design scheme of the system, and then implemented the scheme.Eventually, the validity of the design was demonstrated by experiments.