In this paper, we introduce a coded excitation circuit for medical ultrasonic endoscope imaging system. This circuit is composed of TC6320 and its drive chip. The experiment demonstrates that this circuit can export frequency-adjustable, duration-controllable coded signals, and its voltage reaches +/-60 V. It still works well when excitant frequency reaches 30 MHz. Compared with the conventional medical ultrasonic pulse-echo imaging system, this coded excitation system has the potential of higher SNR and deeper penetration depth, especially for the small emission power system. This method has a bright future.