Harmonics generated from Large-scale Grid-connected photovoltaic plant (GCPV) has the characteristics of high frequency and wide range. So the impact of distributed parameter of high-voltage cables becomes more significant. Based on an actual GCPV, harmonic output particularities were discussed according to its operating mechanism. Step-up transformer, reactive power compensation device, distributed capacitance of transmission line and the loads were considered, the transmission mechanism of harmonics in this network was analyzed by the definition of resonance amplification factor. According to IHAPF (Injection-type Hybrid Active Power Filter), proposed a novel control strategy for resonance suppression. Simulation results verified the theory.