The harmonic sources model of wind grid accessed to power system is established by measurement and statistical methods based on the large scale wind system planning of Gansu jiuquan area. The harmonic power flow is analysed under different operation modes in power system. The harmonic pollution trend of the million kilowatt wind accessed to power system at present stage and 2015 are analysed and compared, the calculation results show that the harmonics pollution is most serious at the point which wind power accessed to the network, the harmonic pollution degree is damping along the line. The farther electrical distance from harmonic sources, the fewer harmonic, and the harmonic pollution is decreasing with the grid structure constantly reinforced. This research will provide reference data for power grid planning and wind power quality management.