LADAR target simulator is the key component of the HWIL system for LADAR，which is designed to simulate the LADAR return projection. One of the key technologies of target simulator is object modeling. The method of object modeling was performed and mathematic models were given based on coordinate transformation. The overall information of target was obtained through data registration on the part of the target information from different angles of scanning. Then according to the viewpoint of coordinate transformation, the target information was obtained by arbitrary viewpoint in the space, which was provided for image generation system to generate an image. Theoretical results agree well with the values measured experimentally. Therefore, the accuracy of modeling was verified by experiment. This method can provide a feasible way for LADAR target simulator to acquire the information of the target.