ccording to the principle of single-beam measurement, using ultrasonic transducer ultrasound wave was launched to the seabed floor. Ultrasonic transducer sent ultrasonic signal as a reference signal,the echo signal was delayed several times. Through continuous adjustment of the quantity of delay time, the minimum mean square (LMS) error was gained between the reference signal and the echo signal. The delay time equals to promulgation time. The product of delay time and ultrasonic wave velocity is the distance between ultrasonic transducer and seabed floor. Computer simulation and test results indicated that using minimum mean square error method to measure seabed microtopography, the high precision can be obtained. It can be applied to the seabed microtopography survey.