Aiming at the requirement of high-precision calibration of light plane for double-line structured light skin seam measurement system, a calibration method of two-line structured light plane based on planar target is proposed. First, take the datum point on the target plane as input, construct the target plane pose solution model, and obtain its plane equation in the camera coordinate system. Then, according to the line surface model of the camera, the depth of the fitting control points is reconstructed. Finally, the eigenvalue method is used to fit the denoised fitting control point set to complete the calibration of double-line structured light plane. Experiments show that this method can simultaneously complete the calibration of two light planes in the measurement system. After calibration, the repeated measurement accuracy of seam gap is better than 0.050 mm, and the repeated measurement accuracy of seam flush is better than 0.030 mm.