A Prandtl transformation method is applied to study the natural convection of non-Newtonian fluids along a wavy vertical plate in the presence of a magnetic field. A simple transformation is proposed, to transform the governing equations into the boundary layer equations, and solved numerically by the cubic spline approximation. A simple coordinate transformation is employed to transform the complex wavy surface to a vertical flat plate ibr a constant wall temperature by the numerical method. The effects of the magnetic field parameter, the wavy geometry and the non-Newtonian nature of the fluids on the flow characteristics and hear transfer are discussed in detail. It is found that the action of the magnetic field is to decelerate the flow, thus decreasing the Nusselt number.