The fill factor (FF) as an important photovoltaic parameter is related to the property of transport layers and active layers for organic solar cells (OSCs). Herein, we propose a simple method to improve FF by using inorganic-organic composite hole transport layer (HTL) in OSCs. Through incorporating inorganic metal oxide, vanadium pentoxide (V2O5) nanoparticles into PEDOT:PSS, the morphology and conductivity of the composite HTL are improved, due to V2O5 nanoparticles can fill the pinholes in PEDOT:PSS and expose more PEDOT chains to the surface core-shell structure. The PTB7-Th:PC71BM-based OSCs with different HTLs were prepared. The power conversion efficiency and FF of the OSCs for the composite HTL can be greatly improved compared with the traditional HTL, which can reach up to 9.44% and 70.14%, respectively. The results of water contact angle and grazing incidence wide-angle X-ray scattering show that the hydrophobicity of the composite HTL is improved, which can not only improve the physical contact but also greatly affect the subsequent active layer formation, thus increasing the crystallinity of PTB7-Th:PC71BM. These results demonstrate that V2O5:PEDOT:PSS has good application prospects as a HTL to realize high-efficient OSCs.