In robotic spray painting, 3D model of workpieces plays an important role, requiring information in geometry and shape for path planning or pose estimation. To solve the problem that it is difficult to effectively acquire a 3D workpiece model in practical spraypainting applications, this paper proposes a fast-modeling method based on complementary perspectives with multiple RGB-D cameras. In this method, two RGB-D cameras installed oppositely are used to acquire the local point cloud of the workpiece in a complementary perspective. Then, a special simple two-sided calibration plate is designed to offline calibrate the external parameters of the camera system based on the idea of coplanar joint optimization of intersection points, which is to accurately estimate the transformation matrix between cameras without coincident field of view. Finally, with the calibrated transformation matrix, the local workpiece point clouds with non-overlapping areas online captured from different camera perspectives are fused into a complete 3D workpiece model. Experimental results show that the proposed method can effectively construct the model of polyhedral workpiece with complicated structure, less than 160 ms of reconstruction time, and below 5. 3 mm of error.