A preparation method of perovskite film based on semicarbazide hydrochloride (SEM-HCl) additive and a preparation method of photovoltaic device are provided, a perovskite optimized crystallization strategy is provided, a tin-based perovskite thin film is prepared based on a solution method, and a purpose of regulating and controlling perovskite crystallization is achieved by means of a cross-linking effect of special groups in SEM-HCl and perovskite components. Defects of crystals of the prepared perovskite film are reduced, the non-radiative recombination in a transmission process of carriers is suppressed, and a photoelectric conversion efficiency and a photovoltaic device stability are remarkably improved.