Lead iodide perovskite (CH3NH3PbI3) is a promising light absorber for high efficiency solar cells, due to its high extinction coefficient, broad absorption spectrum, and excellent electrical properties. Power conversion efficiency (PCE) of perovskite has reached 20.1%. However, the charge recombination in the mp-TiO2 based electron transport layer is still one of the critical factors that hinder the electron transport. Herein, we report reduced graphene oxide (rGO)/mp TiO2 nanocomposite based mesostructured perovskite solar cells that show an improved electron transport property owing to the reduced resistance of the composite layer. The impact of the rGO added to the TiO2 layer on the film resistivity, electron diffusion, recombination time and photovoltaic performances are investigated, thus the amount of the rGO is optimized. Consequently, the rGO/mp-TiO2 nanocomposite, for the mesostructured perovskite solar cells, exhibited the PCE of 14.5%.