The theoretical results are presented for the stagnation zone effect of the slewing laser beam, for the examine，the numerical calculation using 4D code of the laser atmosphere propagation are proceeded. The theory analysis and the results computed by 4D code show that in many cases the influences of the stagnation zone effect are not important because in those cases the beam spreading radius induced by thermal distortion in the stagnation zone is smaller than that induced by the diffraction effect.