Active Queue Management (AQM) based on nonlinear difference equations has been proposed to solve the end-to-end TCP network congestion problem recently. The proposed AQM scheme can guarantee the stability of the multiple bottleneck network by nonlinear control for dropping probability of the routers. Nonlinear control often relies on some heuristics and network traffic controllers that appear to be highly correlated with the multiple bottleneck network state. Based on the proposed nonlinear difference equations for TCP flows control across the network, this paper reveals the reasons of congestion of multiple bottleneck AQM, and provide three theorems for avoiding network congestion. Moreover, we give simulations to verify the results for nonlinear control of the multiple bottleneck network congestion.