Based on the noise of different gradient data, several typical gradient integral algorithms are studied and discussed, an improved Southwell global integral algorithm was proposed. Taking the similarity and root mean square error between the reconstructed surface and the original surface as the performance parameters, the gradient data was simulated. A fringe reflection experiment platform was built to reconstruct the standard concave spherical mirror, and the fringe reflection measurement results were compared with the actual component parameters. The experimental results show that the radius error of the concave sphere reconstructed by the improved Southwell algorithm is 0.09%, the structural similarity is greater than 0.999, and the reconstruction speed is 1.2 times that of the original algorithm. Compared with the traditional integration algorithm, the improved Southwell algorithm achieves higher reconstruction quality and reconstruction efficiency, and meets the requirements of non-contact, high accuracy and strong stability of the mirror object measurement.