Preparation and stability of nanocrystalline (C6H5C2H4NH3)(2)Pbl(4)-doped PMMA films were investigated. By using spin-coating and subsequent annealing technique, nanometer-sized (C6H5C2H4NH3)(2)Pbl(4) precipitates were successfully formed into a PMMA matrix. These films showed clear exciton absorption and free exciton emission at room temperature. Comparing with (C6H5C2H4NH3)(2)Pbl(4) film, marked improvement of thermal- and photo-stability was observed for nanocrystalline (C6H5C2H4NH3)(2)Pbl(4)-doped PMMA films. The thermal- stability of these films correlates with the decomposition of the organic part. As for photo-stability, photo-irradiation induced oxidation is one of the possible reasons for the degradation of the films.