Static time error is an important factor affecting the accuracy of ultrasonic flowmeter, this study proposed a new impedance matching circuit design to suppress the static time error, and finally an ultrasonic flowmeter measurement system with ultra-low static time error is successfully developed. Based on the homemade ultrasonic flowmeter prototype, experiments on static time error were carried out at different driving frequencies, high temperature conditions (200 °C, 230 °C and 260 °C), and the accuracy of the flowmeter was verified by the real-flow calibration bench. The results show that the reciprocal impedance matching circuit can significantly reduce the static time error of the system, with a minimum static time error of −0.278 ns at high temperatures. Finally, through the real-flow calibration test, the ultrasonic flowmeter can achieve an accuracy level of 0.138% at a low flow rate of 440m3/h, and an accuracy of 0.05% in the range of medium and high flow rates of 1500 ~ 4400 m3/h, which verifies the feasibility of the reciprocal impedance matching circuit, and provides a solution for ultrasonic flowmeter with a high accuracy and low static time error.