In this paper, a distributed planning method for EV dynamic wireless charging system (DWCS) is proposed, which determines the locations and the scales of DWCS to maximize the economic effects of wireless charging while meeting EV charging demands. The Nesterov's model with multiple traffic patterns is adopted in the traffic network (TN) to solve the traffic assignment problem and the traffic wave theory is used to analyze the distribution of road traffic density. In power distribution network (PN), the effect of EV connection modes on the expansion cost of power lines is considered. A mixed-integer linear programming (MILP) model for the proposed planning problem of DWCS in coupled power-traffic networks (PTN) with PN and TN constraints is formulated and solved with MATLAB/CPLEX. The DWCS case studies are carried out to verify the effectiveness of the proposed distributed planning method in PTN.