In order to achieve the comprehensive monitoring of on-road vehicle emissions in urban areas, the road network vehicle emission remote sensing system is constructed. In the system, the location of remote sensing detectors has a great effect on the effectiveness of monitoring on-road vehicles. Thus the location of detectors is a key factor in the construction of road network vehicle emission remote sensing system. In this work, a location strategy based on the topology structure of traffic network is proposed. First, a mathematical model for the problem of interest is established, where the connection degree between road sections is described with the aid of the reachability matrix of the line graph of the traffic network graph. Then, a dual structure code based genetic algorithm is employed to obtain the solution. The experimental results show that the proposed location strategy in this work can capture more individual vehicles in the road networkthan the traditional schemes.