Proposed in this paper is an optimal arrangement method of traffic flow detectors based on the correlation of link flow in the road network.In the investigation,first,the number of key links is determined by using the link-path incidence matrix and its dependence on the network scale,the network connectivity,the number of OD pairs and the path number is analyzed.Then,by taking into consideration such factors as path coverage,road grade,road length and road facilities,a multi-objective optimization model for the selection of key links is set up,and a method determining the non-key link flow through the linear combination of key link flow is proposed.Experimental results on Nguyen-Dupuis network show that the proposed method is of good practicability.