Abstract: The piezoelectric ceramics of little capacitance have a simple hysteresis,for which a special mathematic model with least square method can be established,using the data obtained by a particular experiment system.Then a computer program based on the model makes the open loop control to tiny displacement system of detecting apparatus based on white-light interference technique.The total displacement length is 20μm and the precision reaches 0.03μm.In addition,the flow chart of the program is given.