The invention relates to a Bi1-xSmxFe0.94Mn0.04Cr0.02O3 ferroelectric film with high remanent polarization and low leakage current density and a preparation method thereof. The method comprises the steps of dissolving bismuth nitrate, ferric nitrate, samarium nitrate, manganese acetate and chromic nitrate into mixed ethylene glycol monomethyl ether according to the mole ratio of (1.05-x): x: 0.94: 0.04: 0.02, then, adding acetic anhydride, and adding ethanolamine to adjust viscosity, so as to obtain a Bi1-xSmxFe0.94Mn0.04Cr0.02O3 precursor solution with the metal ion concentration of 0.003-0.3mol / L; uniformly dispensing the Bi1-xSmxFe0.94Mn0.04Cr0.02O3 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 Bi1-xSmxFe0.94Mn0.04Cr0.02O3 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, the remanent polarization of the film is increased greatly, and the leakage current density of the film is reduced effectively.