The wake concentration fields of a cylindrical hydraulic structure with different pollution source locations(upstream and downstream of the structure)were simulated using the Reynolds equation and RNG k-ε turbulence model. The effects of pollution source locations on the distribution of pollutant concentration downstream of the cylindrical hydraulic structure were investigated from three aspects: the time-averaged pollutant concentration, the fluctuation intensity of concentration, and the half-concentration width, which is the distance from the central line of the wake flow to the position with half of the maximum concentration. The results show that with the increase of flow path length, the transverse distribution of time-averaged pollutant concentration experienced three stages, i. e. , the bimodal structure, transition stage, and Gaussian distribution. When the pollution source was located upstream, the concentration fluctuation intensity first increased and then decreased; when the pollution source was located downstream, the concentration fluctuation intensity decreased continuously. The variation of the half-concentration width shows the same trends for the two pollution source locations: a nonlinear increase trend when 1≤x/D<15 and a linear increase trend when 15≤x/D≤30.