A simplified thermal lattice Boltzmann method (STLBM) is proposed in this paper.

It is derived from macroscopic equations recovered from lattice Boltzmann equation.

It is shown theoretically and numerically that STLBM is unconditionally stable.

As compared with conventional thermal LBM, STLBM needs much less virtual memory.

STLBM can well simulate incompressible thermal viscous flows.