In order to obtain the information of elevation which threedimensional reconstruction needs in the spotlight mode inverse synthetic aperture ladar imaging, a target reconstruction algorithm was designed based on spotlight mode inverse synthetic aperture imaging ladar groups. The systems were placed inverse synthetic aperture ladar in the three vertices of an equilateral triangle. According to the relationship between the position and the inclination angle, the elevation information for reconstructing threedimensional target could be provided by another two ladars. The elevation functions of three inverse synthetic aperture ladars were calculated when the measured target flied into detects area of the system in any direction. Simulation result shows that the speed of the measured target has no significant effect on the elevation function. Angular relationships of inverse synthetic aperture ladar and target have a significant contribution to the changes in elevation information. In the process of information fusion for different position elevation, the selection of distributed manner for inverse synthetic aperture ladar impacted the utilization of echo data. Because different angles change produces continuous changes in elevation information, this method can effectively reconstruct target threedimensional image by elevation information obtained.