A displacement sensor with controlled measuring force and its characteristics analysis are discussed in this paper. The displacement sensor consists of an electric induction transducer with high resolution and a voice coil motor (VCM). The measuring principles, structure of the sensor are discussed. Theory model, dynamic and static characteristics of VCM are analysed. A measuring system for surface topography with large measuring range is constructed based on the displacement sensor and 2D moving platform. Measuring force of the sensor in measurement process of surface topography can be controlled at μN level and hardly changes. It has been used in measurement of bearing ball，bullet mark, etc.