Based onαβ coordinate system， the variable-step adaptive algorithm is applied to detect the reactive current and harmonic current of non-linear loads. Using the amplitude of each harmonic current as weight of the adaptive iterative algorithm， the low-order harmonic currents' impact on convergence value of step and weight factor can be basically eliminated， so as to guarantee the detection accuracy. The parameters of proportional resonance（PR） controller are designed based on the PI controller's parameters. The reactive fundamental current and the low-order harmonics can be controlled to be zero-steady-error by the relevant PR controller respectively. The effectiveness of the proposed algorithm and design is validated by the simulation and experimental results.