In this work, the resolution and measuring range of the Horn-Schunck global optical flow algorithm and Lucas-Kanade local optical flow algorithm in fringe displacement measurement are analyzed. The simulation results show that when the relative error of the Horn-Schunck algorithm and Lucas-Kanade algorithm is less than 2%, and the resolution of Horn-Schunck algorithm and Lucas-Kanade algorithm can reach 10 ^-13π. Furthermore, the corresponding displacement resolution on image plane is 1.6×10 ^-12 pixel. This shows that the resolution of the two algorithms is consistent with that of the four-step phase shift method. In the case of noise, the resolution of both algorithms reaches 0.01π, and the displacement resolution of the corresponding image surface is 0.16 pixel. When the relative error is less than 2% and the root-mean-square error is less than 3%, the measurement ranges of Horn-Schunck algorithm and Lucas-Kanade algorithm are 0--17π/100 and 0--52π/100, approximately 0--π/6 and 0--π/2, respectively, and the measurement ranges are less affected by noise.