The effects of deposition temperature (500-800 degreesC) on the structural defect and electrical resistivity of heteroepitaxial La0.5Sr0.5CoO3 (LSCO) films with CeO2/YSZ double buffer layers on Si(001) substrates have been investigated mainly by high-resolution x-ray diffraction techniques. According to the deposition temperature range, two types of structural defect could be distinguished clearly. In the lower-temperature range of about 500-600 degreesC, the main defect of LSCO is the mosaic structure with a huge coherent distortion. In the higher range of about 600-800 degreesC, a distinct lattice constant gradient of LSCO was observed, indicating an occurrence of lattice relaxation when introducing an additional defect type, which are misfit dislocations. A high correlation between the electrical resistivity of LSCO, and the defect type and concentration was found. The distribution of electrical resistivity shows a mosaic dispersion degree dependence in 500-600 degreesC and a lattice relaxation degree dependence in 700-800 degreesC, where the mosaic dispersion degree and lattice relaxation degree can be estimated by the full width at half maxima of omega and 2theta/omega scans, respectively.