The directional accuracy of threatening laser is highly dependent on the laser spot center location accuracy for the imaging laser warning system. The spot features of wide field-of-view fish-eye imaging laser warning system are analyzed. As the low fill factor of CMOS sensor and the energy distribution asymmetry of spot in big incident angle region will affect the location accuracy of spot center, an improved algorithm is proposed. Firstly, it separates the two-dimensional Gaussian function integral of pixel intensity readings into a product of two one-dimensional integrals. Then the Gaussian function integrals which are difficult to solve even by numerical means are inverted using an error function approximation approach. Finally, the spot center coordinates are derived in terms of the intensity ratios of neighboring pixels. The accuracy and stability are verified and compared with traditional algorithm by experiment. The experimental results show that this method can reduce the location error caused by incomplete fill ratio of CMOS pixel and large unsymmetrical optical aberration of fish-eye lens. The spot positioning precision in paraxial region and big incident angle region are 1/80 and 1/70 pixel, respectively. The maximum error is less than 1/30 pixel. It can satisfy the system requirements of laser warning equipment, including real time, higher precision, as well as strong stabilization for spots in different areas of CMOS sensor.