This thesis aims at modeling a special system, which can be described in this way : The control system is to controling the light-quality object in the sealed pipeline.(eg: ping pang balls).The fan connected with the pipeline at the bottom of the model, is used to control the suspended -height of the object in it. And the Nonlinear Infrared is used as the measuring instrument. Thus ,the input is the fan's working volt; the output is the object's height. This thesis set models for PWM Regulator, fan, air pipeline ,Nonlinear Infrared and other programs successively. And give us a settlement of achieving the parameter of each programs . This article adopts linear treatment to settle the system and peripheral equipment to acquire the parameter. This essay mainly provides a method for the modeling system and it has redeeming feature for the model building of every mini system.