A new convenient calibration algorithm is proposed for unsynchronized multi-camera networks having large capture volume. The proposed method gives a simple and accurate calibration mean using a small 3D reference object. Extrinsic and intrinsic parameters are recovered simultaneously by capturing the object placed arbitrarily in different locations in the capture volume. The proposed method first solves the problem linearly with factorizing projection matrices into the camera and the object pose parameters. Due to the multi-view constraints imposed on the factorization, the consistency of rigid transformations among cameras and objects can be acquired. These consistent estimation results can be further refined by a non-linear optimization process. The proposed algorithm is evaluated via simulated and real experiments to verify that it is more efficient than previous methods.