Optical coherence tomography intravascular ultrasound （OCT-IVUS） imaging can compensate for the low imaging depth of optical phase interference imaging and the low resolution of ultrasound imaging， and can comprehensively identify vulnerable plaques in blood vessels. However， due to the limitation of the IVUS ultrasound transmitting repetition frequency， it is difficult for OCT-IVUS imaging to ensure a large number of A-line acquisitions while performing high-frame-rate imaging， thereby limiting the display resolution. To improve the imaging speed of IVUS without reducing the resolution of image display， a high-repetition ultrasound excitation method is applied to solve this problem. Here， an ultrasound transmit circuit with a 50 kHz repetition frequency is designed to improve the imaging speed of IVUS， and a high-speed ultrasonic endoscopic imaging system with 50 f/s is developed based on this circuit. The high-voltage pulse test and the signal noise ratio （SNR） test proved that the transmit circuit is able to excite a 25 MHz transducer while obtaining a signal with high SNR. The transmit circuit can be used for the excitation of 25 MHz ultrasound transducers and has a high SNR； the ultrasound endoscopic imaging system developed by the application of this excitation circuit can increase the imaging speed without reducing the display resolution. The system has clinical application value for improving the effective use of OCT-IVUS， early detection， diagnosis， and prevention of cardiovascular diseases， and has a promoting effect on the detection of vulnerable plaques.