In the present article Williamson nano fluid flow over a continuously moving surface is discussed when the surface is heated due to the presence of hot fluid under it. Governing equations have been developed and simplified using the suitable transformations. Mathematical analysis of various physical parameters is presented and the percentage heat transfer enhancement is discussed due to variation of these parameters. We employed Optimal homotopy analysis method to obtain the solution. It is presented that initial guess optimization will provide us one more degree of freedom to obtain the convergent and better solutions.