With the continuous improvement of wind power penetration, the impact of wind uncertainty and intermittence on power grid protection schemes is increasingly significant. A protection setting scheme based on a fixed threshold is no longer suitable for complex and changeable power systems. In view of this, this paper proposes an adaptive threshold differential protection scheme for a power grid with large-scale wind power based on positive sequence current. First, taking the standard power system with a wind farm as an example, the influence mechanism of wind power "T" access on traditional current differential protection is analyzed. Then, taking positive sequence current as the fault signal and taking the fault location and occurrence time as independent variables, an adaptive threshold differential protection model is established. In order to improve the solution efficiency to meet the requirements of protection control, a two-stage solution method based on a PSO algorithm is proposed. In phase 1, the fault type with the highest impact on the threshold is obtained by taking the fault location as the optimization variable; phase 2 introduces the fault start time on the basis of phase 1, and carries out two-dimensional optimization only for the fault types obtained in phase 1. This can significantly shorten the calculation time, so as to realize the rapidity and accuracy of threshold calculation. Finally, the correctness and effectiveness of this method are verified by simulation analysis based on Matlab. This work is supported by the National Key Research and Development Program of China (No. 2016YFB0901300).