The weaving sections often turn into the bottleneck on the elevated roads. On the basis of the NS cellular automaton traffic model, the weaving section with one-lane main road was simulated and analyzed. For the free traffic flow, weaving almost has no influence on the system, even with increased weaving length. On the other hand, when the traffic flow is in congested state, weaving conflicts have negative effects on the system. The traffic condition will be improved with the increase of weaving length. Our simulation results suggest that the length of weaving sections need not to be inappropriately increased, and a proper moderate value should be chosen to get an optimal traffic condition.