In order to improve the accuracy of optical tracker,the macro pixel method is used for estimating initial target region.A term,valid pixel ratio,is put forward and then is applied to analyze the effects of noise and asymmetry on the location for initial target region.Finally,the most macro pixels and the restricting operation way with high-precision and strong anti-noise ability are obtained.For the unsymmetry target of 4 pixel×4 pixel in 128 pixel×128 pixel spot image,the most macro pixel is 36 pixels and target macro pixel is enlarged by 2 pixel.The value of r is 1 when SNR is 5 dB.Dynamic picture test shows that the method has the processing speed of 18～20 frame/s.