A perovskite solar cell based on carbon quantum dot doping antisolvent passivation grain boundary defects and a preparation method thereof belong to the technical field of perovskite solar cells. Theperovskite solar cell comprises ITO conductive glass substrate, PEDOT: PSS hole transport layer, carbon quantum dot doped antisolvent perovskite active layer, C60/BCP composite electron transport layer, Ag anode, and toluene antisolvent doped with carbon quantum dot is added dropwise in the preparation process of a perovskite active layer. The invention synthesizes environmentally friendly carbonquantum dot materials by a hydrothermal method, a certain amount of thecarbon quantum dot materials are introduced into the toluene antisolvent, perovskite thin film by antisolvent cleaning in the process of spin-coating growth of perovskite active layer, a certain amount of carbon quantum dot materials are introduced in the perovskite thin film by utilizing antisolvent cleaning. The carbon quantum dot is used to passivate the grain boundary defects, eliminate the ion transport in the thin film, and then eliminate the phenomenon of light wetting. At the same time, the high conductivity of carbon quantum dots is used to improve the conductivity of perovskite thin films and the carrier transport, and then the device performance is improved.