Abstract: Angular blocking dips around the <110> axis in A1 single crystal of α-particles of about 2Mev produced at a depth of 0.2uuuuuuuuuuuuuum are calculated by a Moute-carlo simulation.The influence of the small solid angle emission of particles and the importance sampling in the solid angle emission have been inve-stigated.By means of importance sampling,a more reasonable results with high accuracy are obtained.