In this paper, the problem of steady laminar two-dimensional boundary layer MHD flow and heat transfer of an incompressible viscous fluid with the presence of buoyancy force and viscous dissipation over an vertical nonlinear stretching sheet with partial slip is investigated numerically. Numerical solutions of the resulting nonlinear boundary value problem in the case when the sheet stretches with a velocity varying nonlinearly with the distance is carried out. The effects of for various values of suction parameter, magnetic parameter, Prandtl number, Eckert number, buoyancy parameter, nonlinear stretching parameter and slip parameter on flow and heat transfer characteristics is investigated.