Abstract: Tnis paper introduces the results of computation of the filters （LP filters） for 11-element barker code, which reduce the level of maximal side-lobe level to minimum, and the filter performances affected by the dopp-ler shift. When the length of the LP filter is 53, the sidelobe level is reduced to -39.5 dB and it is 18.7 dB better than that by matched filter. The computations of the LP filters with weigthing sequence lengths （L） of 41, 45, 49 and 53 for the 11-element Barker code show that the effects of the doppler shift on the performances are presented, as the degradation and widening of the mainlobe level, the raise of the minimal side-lobe level, the raise of the sum of mean square of sidelobe levels and the increasing the loss of the signal to noise ratio. In smaller doppler shift （fd）, the performances of the LP filter with large L are better than one's with small L. But these superiorities diminish gradully and the performances of the filters with different lengths roughly are unanimous as the doppler shift increases.