The invention relates to a BiFe0.96-yMn0.04CryO3 ferroelectric film with high remanent polarization and high dielectric constant and a preparation method thereof. The method comprises the steps of mixing bismuth nitrate, ferric nitrate, manganese acetate and chromic nitrate according to the mole ratio of 1.05: (0.96-y): 0.04: y, then, dissolving a mixture into mixed ethylene glycol monomethyl ether, and then, adding acetic anhydride, so as to obtain a BiFe0.96-yMn0.04CryO3 precursor solution with the metal ion concentration of 0.003-0.3mol / L; uniformly dispensing the BiFe0.96-yMn0.04CryO3 precursor solution on a FTO / glass substrate, of which the surface reaches atomic cleanliness, by adopting a spin-coating method, so as to prepare a film, then, drying to obtain a dry film, and then, adopting a layer-by-layer annealing process, thereby obtaining the crystalline BiFe0.96-yMn0.04CryO3 film. The method has the advantages that the requirements for equipment are simple, the experimental conditions are easily met, the prepared film is relatively good in uniformity and easy in doped amount control, and the ferroelectric properties and dielectric properties of the film can be improved greatly.