This paper presents a simulation and calculation for the hysteretic delta-sigma modulator (HDSM). A complete theoretical study of the significant modulator parameters is also given. The HDSM structural design has three characteristics appropriate for the high-speed A/D conversion: (1) all signals contained by the modulator are positive for a specified enclosed input; (2) no sample-and-hold switch necessary for the reason that of using a bi-stable switch with hysteresis; (3) the input signal has almost a linear relationship with the time-averaged output.