Stimulated Raman scatting (SRS), which is one of the parametric processes of laser-plasma interactions, is examined by an explicit, electromagnetic, relativistic kinetic particle-in-cell code in one dimension. The code algorithm and implementation details are discussed. It is found that kinetic effects are important to SRS instability. Time-averaged reflectivity onsets at threshold intensity, and saturates at higher intensity. Backward SRS bursts in sub-picosecond, periodically. Kinetic ions initially delay the growth of SRS. Electron trapping results in the SRS bursts. The saturation of SRS results from the nonlinear frequency shift of Langmuir wave. Work is underway to add binary Coulomb collision to parallelize it, and to extend the code to 2D3V.