The laser spot image quality is one of the important indexes for laser guided weapons,but traditional sub pixel location algorithm often has some problems such as poor anti interference capability,low location precision and complexity of software realization.In order to realize the measurement of precise laser spot center,an improved weight interpolation sub pixel algorithm is proposed.All effective image pixel nodes within the laser-spot collected with CCD are grouped and interpolated respectively,and then the calculated results of each group are weighted to achieve high locating precision and stability.By error analysis and experiments,this algorithm can improve the location precision and anti-interference performance efficiently.