Lattice Boltzmann thermal models with second-order accuracy are obtained with an extra parameter term.They are employed to Rayleigh-Benard convection heat transfer and are compared with original models.In order to reduce error of Nu number at large Ra number and thermal diffusivity,we analyze truncation error of corresponding heat-transfer equation and introduce an adjusting parameter in the equilibrium distribution function.Applicability of LBM heat-transfer models is extended.