The imaging characteristic of omni-directional laser detecting system is introduced,and two algorithms of subpixel measurement are put forward.The two algorithms are respectively barycentre method and elliptic fitting method.The theoretical analysis and experimental verification were carried out with the two algorithms.The mean value and standard deviation of the spots′ coordinates with different size were obtained.The result shows that:the locating precision of barycentre method is high when the laser spot is small,and precision of elliptic fitting method is high when laser spot is large.Thus,in order to heighten the system′s locating precision,a comprehensive method,which automatically selects one of the two algorithms according to the size of laser spot,is put forward.The experiment data indicates that the comprehensive method has high locating precision,which can be under 0.15 pixels.The result of this work is helpful for the study of precise determination of threatening laser direction.