The resonance fluorescence of thin crystal films is studied by the method of Heitler and Ma, with the resonant interaction between the crystal and the radiation field properly taken into account in a nonperturbative way. Owing to the violation of the lattice symmetry by the thin film geometry, it is found that not only the usual polariton type eigenstates characteristics of a bulk crystal cannot be found, but the crystal film once excited by the absorption of a photon will fluoresce with a superradiatively enhanced rate as a consequence of the coherent action of the atoms within roughly a wavelength of each other. Absorption and emission spectra are given explicitly.