Intra-operative navigation in which the target position is provided to assist an intuitive understanding of the surgical field has been studied and applied in many clinical areas. Position measurement of a surgical field is usually performed with a magnetic sensor, a marker type optical position sensor. For navigation of hard tissue, the measurement of several markers dispersedly located on the surface is enough to detect the position of an object that can be assumed as a rigid body. However, for the navigation of soft tissue such as skin and liver, a sensor that can measure the deformation of the object surface time-sequentially would be essential. We have developed a 3D visualization system for surgical field deformation with geometric pattern projection. In an animal experiment, the registration of preoperative 3D organ model could be done with the time-sequentially updated surface deformation data. In the video image of surgical field, the inner structure model of organ could be superimposed successfully.