A laser stripe sensor has two kinds of calibration methodologies. One is based on the homography model between the laser stripe plane and the image plane, which is called the one-step calibration methodology. The other is based on the simple triangular methodology, which is named as the two-step calibration methodology. However, the geometrical meaning of each element in the one-step calibration methodology isn’t clear as that is the two-step calibration methodology. A novel mathematical derivation is presented to reveal the geometrical meaning of each parameter in the one-step calibration methodology, and then the comparative study of the one-step calibration methodology and the two-step calibration methodology is completed and the intrinsic relationship is derived. What is more, an improved one-step calibration methodology is proposed with 7 independent parameters rather than 11 independent parameters. Experiments are conducted to verify the accuracy of their comparison and robust of the proposed calibration methodology.