The invention belongs to the field of functional film materials and specifically discloses a bismuth-molybdate-based transparent ferroelectric light-emitting film and a preparation method thereof. The chemical composition of the bismuth-molybdate-based transparent ferroelectric light-emitting film is (Bi<2-x>Ln)MoO<6>, Wherein Bi<2>MoO<6> is the base material, Ln is one of rare earth elements, namely Eu, Pr, Er, Tm or Yb, and x in the formula is greater than 0 and less than or equal to 0.50. The bismuth-molybdate-based transparent ferroelectric light-emitting film maintains the ferroelectric properties of a bismuth-molybdate film, the good photoluminescence characteristic is achieved, and the film can be excited by ultraviolet light or 980 nm lasers to emit visible light which is visible to naked eyes; the preparation method of the bismuth-molybdate-based transparent ferroelectric light-emitting film is simple and easy to implement, and no vacuum equipment is needed.