Abstract: The basic parts of the distance measurement of a pulse echo system were described. The study of lower noise electronic circuits was emphasized in the ranging system. A new kind of emitting and receiving circuit was designed with an isolated switching circuit to form different switching times and isolated current circuits, and the routing of the electronic noise from the emitting circuit to the receiving circuit was totally isolated. The new principle of "energy ball" was proposed to increase the signal-to-noise ratio distinctly, and the ability of receiving echo signals is more stable in the normal power consumer. Also a software filter in the digital data base of the pulse echo was introduced in the application to intelligent noise reduction.