Abstract: The control of output impedance of grid-tied inverters is investigated to reshape the impedance network of the distributed photovoltaic（PV） system. Firstly, in the view point of a typical distributed PV system, the series and parallel harmonic resonances in single LCL-based grid-tied inverter and multiple inverters are studied. Besides, the factors that influence on resonances are also quantified. Then, a control strategy is proposed to maintain the impedance of a grid-tied inverter to damp the harmonic resonances in the PV system. In the presented control scheme, with the aid of virtual impedance gain, the output voltage and current of the grid-tied inverter are filtered by Second-Order-Generalized-Integrator based notch filter and fed to reference current part and modulation part, respectively. The introduced virtual impedance can damp the possible harmonic resonances in the cases of virtual resistors are employed. Additionally, the effectiveness of the virtual resistors on resonances damping is also depicted and checked. Finally, simulated results performed on PSCAD/EMTDC and experimental tests from a micro-grid demonstration are indicated to verify the validation and feasibility of the proposed control strategy.