The invention discloses a method for preparing Bi4-XLaXTi3O12 ferroelectric film by microwave solvent thermal process. First, Bi(N03)3.5H2O and La(NO3)3.nH2O are put into glycol to generate solution A; second, the solution A is dropped into the butyl titanate stabled by acetylacetone to generate solution B; citric acid is added into the solution B to generate solution C; third, the solution C is poured into a microwave hydrothermal reactor, a glass substrate is put to the bottom of the microwave hydrothermal reactor to seal the reactor and the reactor is put into a MDS-6 type temperature and pressure double-control microwave hydrothermal reaction instrument; fourth, the temperature control mode of the reaction instrument is selected for the reaction and the reaction instrument is cooled to room temperature after the reaction is ended; fifth, the reactor is opened, the glass substrate is taken out, washed for several times respectively with deionized water and anhydrous alcohol, and dried in an electrothermal blast drying oven, then the final product Bi4-XLaXTi3O12 ferroelectric film is formed on the glass substrate. The invention uses the microwave solvent thermal process to quickly prepare the Bi4-XLaXTi3O12 ferroelectric film on the glass substrate; the reaction is completed in the liquid phase for one time, needing no sequent treatment; the technological equipment is simple, the Bi4-XLaXTi3O12 ferroelectric film is even and the reaction period is short.