The unsteady MHD mixed convection flow past an infinite vertical porous plate embedded in a porous medium in the presence of thermal radiation and chemical reaction with viscous dissipation, heat source and soret effect have been investigated. The governing equations for this investigation are solved analytically using two-term harmonic and nonharmonic functions by Perturbation technique. The effects of various parameters like Radiation parameter, Soret number, Schmidt number, Chemical reaction parameter and Prandtl number on the velocity, temperature and concentration fields have been examined with the help of graphs. The Skin friction, Nusselt number, and Sherwood number are also derived and discussed through tables.