In order to solve the uncertainty of azimuth in the ultrasonic sensor measurement process， a target distance and azimuth measurement method based on time of arrival （TOA） is proposed， and an environment sensing method based on ultrasonic detection is developed. The echo signal is processed based on the mixed Gaussian fitting， which eliminates the problem of signal crosstalk and improves the measurement accuracy of target distance and azimuth information. Based on the characteristics of the sensor beam angle， the simultaneous measurement of targets at different distances is achieved. By introducing “uncertainty”， a set of belief assignment functions is defined， and the DSmT（Dezert-Smarandache Theory） method is used for data fusion to realize map updates. Finally， the experimental device and environment are constructed for verification， and the result shows that the basic contour of the environment can be built through 135 measurements， and the mapping error is less than 3 cm.