A new method to detect and correct the phase errors of laser arrays is presented. This method, based on finding the brightest point of the diffraction pattern, can be used to detect both piston errors and tilt errors. The principle of this method is described theoretically. A system combining two laser beam arrays is built based on active segmented mirrors to testify the efficiency of the method. The experimental results show that the root-mean-square (RMS) value of the piston errors can be controlled in λ/19 and the tilt errors can be controlled in 25 μrad (0.5 times of the diffraction limit). The experiments prove that the new method can be used to detect the phase errors in coherent beam combing of laser arrays.