According to the problem that the performance of grid-connected inverter system is poor due to the limited parameter selection of integer-order PID controller, this paper propose a fractional-order control strategy of grid-connected inverter based on modified particle swarm optimization (MPSO) algorithm. The influence of λ, μ of fractional-order PIλDμ controller on the dynamic and steady performance of the controlled system is analyzed. The PIλDμ controller is combined with current dual-closed-loop and grid voltage feed-forward control, a current control strategy of grid-connected inverter based onPIλDμ controller is proposed and compared with the PID control strategy. The parameter range of PIλDμ controller is analyzed in detail, and the MPSO algorithm is used to optimize the parameters. The simulation results show that the PIλDμcontrol enhances the flexibility of the control system, reduces the total harmonic distortion rate of the grid-connected current, and improves the dynamic response speed and anti-interference performance of the system.