This paper proposes a flexible method of camera calibration:placing two collinear points with a fixed end point (1D object) which is captured by multi-camera systems. By moving the 1D object around the fixed point,all the cameras'' parameters related to a coefficient of radial distortion can be calibrated easily. The calibration objects are simple to make and can be perfectly observed from any orientations. With these merits, the method is practical to calibrate the multi-camera systems. Experimental results show that the calibration is of high precision and convenience.