This paper describes the design of a kind nuclear gauge union function instructional meter, for experiments with three types of nuclear gauge-including level gauge, density gauge and thickness gauge. Hardware design and software design are introduced. Hardware design involves the system construct and circuit principle design of signal processing module (SPM) based on the TMS320LF24 series DSP chip. The SPM is made up of power supplier conversion circuit, clock and reset circuit, liquid crystal displayer circuit and PC interface circuit. Relied on the DSP chip, the speed of SPM on digital signa...