A hand-eye calibration method based on auxiliary target is proposed. In this method an auxiliary target is appended to the camera holder which connects the cameras to the end effector of a robot. The pose parameters of the auxiliary target are measured by laser tracker. The measurement error is estimated and corresponding auxiliary target weights are defined based on the fact that the rotation angle of different coordinate system on the same rigid body should be equal. Then the weights are introduced to improve the redundant hand-eye constraint equations. Finally, the hand-eye equations are solved by weighted least squares method. The calibration result produced by proposed method is closer to data with smaller measurement error and more reliable.