Based on single harmonic current extracting, the paper proposed a control method of grid current and load-side current double-fed composite detection for shunt active power filter. In synchronous rotating coordinate system, the results of the grid current I adjustment feedback and the load-side current P adjustment feedback are integrated. Meanwhile, the harmonic components of the current are extracted as APF compensation command. By constructing the equivalent circuit and the transfer function, dynamic performance and steady-state performance of the control method are analyzed, which can be proved that the influence of control delay, hardware delay and sampling accuracy on compensation effect caused by will be decreased greatly, as well as the system response speed is ensured. Thus the result of zero static error compensation can be achieved. A 380 V/200 A APF prototype is developed to verify the control method of double-fed composite detection.