In this paper, magnetohydrodynamic laminar forced convection of nanoliquid in a rectangular channel with an extended surface, top moving wall and three cylindrical blocks is numerically studied. The Lattice Boltzmann method is used for the resolution of the governing equations. Validity of the numerical home elaborated FORTRAN code was made and good agreement was found with published results. It is interspersed in this work by the effects of the following parameters: Reynolds number (50≤ Re≤ 200), Hartmann number (0≤ Ha≤ 50), nanoparticles volume fraction (0≤ φ≤ 4%) and Eckert number (0.25≤ Ec≤ 1). The numerical solution shows that the local and average Nusselt numbers ameliorate when the value of Reynolds number, Eckert number, and the nanoparticles volume fraction are enhanced. But decreases when the Hartmann number is increased. The impacts of viscous dissipation on heat transfer rate and entropy generation are more noticeable in the presence of a magnetic field. The addition of 4% of nanoparticles enhances the local Nusselt number by about 7%.