La 0.67 Sr 0.33 MnO z (LSMO) thin films were prepared by means of metal–organic decomposition on amorphous quartz substrates under different annealing process. X-ray diffraction spectra show that proper crystallization temperature of the films is beyond 873K and all samples annealed at 953K or above present polycrystalline structure with [202] preferred orientation. Higher annealing temperature or longer annealing time lead to growth of larger grain. Regardless of the difference of grain size, all polycrystalline films present similar and steady magnetotransport properties, such as enhanced magnetoresistance (MR) effect below metal–insulator transition temperature and approximate MR ratio under same applied field, which were ascribed to the porous structural characteristics in the films observed by an atomic force microscope. Additionally, at room temperature the resistivity of each polycrystalline film presents linear change over wide range of applied field and get MR ratio near 5% under 10kOe field.