Aiming at the problem of laser noncoplanar error encountered in the full section measurement of rail profile, a laser noncoplanar error correction model based on projection transformation is proposed, the principle and steps of error correction are described in detail, and the effectiveness and accuracy of the proposed method are verified by experiments. The proposed method reduces the rail profile measurement error caused by noncoplanar laser installation to less than 0.10 mm. This method does not require the laser planes on the left and right sides of the rail to be perfectly coplanar, but only that they be roughly aligned. It not only ensures rail profile measurement accuracy, but also greatly reduces the requirements for component processing accuracy and on-site installation environment, and avoids the time-consuming and labor-intensive laser plane fine adjustment process on site.