In this study, a newly-developed Eulerian gridless solver for simulating two-dimensional unsteady incompressible viscous thermal flows in low Reynolds number is introduced. The Boussinesq approximation is applied to deal with heat transfer and spatial derivatives of governing equations are solved by WMLS(Weighted Moving Least Square) interpolations on a cloud of points. A fractional time step method is adopted and the Poission equation for pressure are solved by successively in a WMLS sense. Some heat transfer problems are solved by the developed solver for the validation and the results are compared with analytic solution and those from other CFD simulations.