Abstract: This paper described a kind of ultrasonic ranging system which employs a new driving circuit and low-noise programmable amplifier. The design of signal-to-noise ratio (SNR) in the circuit was raised to make measurement more stable and reliable. An efficient central ellipse algorithm for estimating the echo peak positions of ultrasonic sampling was presented to find the accurate receive time of echo by searching the peak of energy bursts, which is base on the theories of energy centrobaric correction method and least square method in the ultrasonic ranging system. A comparison of experimental results shows that the proposed algorithm's relative error is approximately 0.2%, which is more accuracy than the envelope detector or the cubic fitted multiple regression equation method, as a result it is suitable for higher accuracy industrial applications.