This paper presents a roll angle calibration method for phased-array radar. Based on the built-in elevation calibration methods of phased-array radar， the proposed method utilizes the approximately linear relationship between the roll angle and the target’s elevation measurement error to calculate the roll angle. Experiments confirm that the roll angle calculated by this method has nearly the same accuracy as that of the method using laser measurement instruments. With the proposed method， the angle measurement accuracy of phased-array radar can be greatly improved.