In order to apply the traditional phase measuring profilometry (PMP) to on-line 3D inspection, Stoilov’s algorithm is introduced. However, the formula of the original Stoilov’s algorithm includes evolution and division operators, and it is quite sensitive to the digitized influence of digital light projector or CCD camera and the disturbance of the surrounding light, which leads to serious phase computing errors inevitably. Therefore, an improved algorithm based on the Stoilov’s algorithm is proposed in detail. The moving step S can be calibrated by pixel matching and the stripe period length L can be calibrated by computing the discrete phase with standard PMP, then the phase-shift quantity Δ can be calibrated, so as the sin Δ. The phase computing error can be minished in effect and the precision of on-line inspection can be improved. In order to verify its feasibility and validity, the experiments are carried on. They show that in on-line 3D measurement the reconstructed 3D object appears visible distortion with the original algorithm but remains fidelity with the improved algorithm instead.