BGP protocol routing update has a large amount of calculation, when the network occurs routing shock in the BGP protocol, the computational complexity would increase rapidly. In order to study the anti shock performance of BGP protocol, has take the low rate denial of service attack as the source of the shock, and studied the selection of the critical paths in the BGP routing topology deeply. Focus on the typical BGP shock attack algorithm as the reference sample, studied the improved method of attack, and analyzed the performance of the BGP protocol by the experimental simulation.