Molecular dynamics simulations of stress relaxation and dynamic loading of isotactic polypropylene have been studied using full atomistic model. Curves of relaxation, used to evaluate the relaxation parameters, show agreement with experimental results. The relaxation time is calculated from the simulated stress relaxation curve. The dynamic loading curves show that stress leads strain as proposed by other theoretical models. Storage modulus, loss modulus and loss factor have been calculated. Despite limitations of smaller simulation time, the results are in comparable range with the experimental values. The length scale limitation of MD simulation is taken care of by the use of periodic boundary conditions. The effect of temperature and the polymeric chain length on the viscoelastic relaxation parameters are investigated.