In this paper, the forced convection heat transfer of Ag–MgO/water hybrid micropolar nanofluid in a channel is studied numerically which the top wall of channel is smooth and bottom of it is in stairway form. The lattice Boltzmann method (LBM) is used for solving the fluid flow and heat transfer equations. The effects of Reynolds numbers ([Formula: see text]–400), volume fraction of nanofluid ([Formula: see text], 0.01 and 0.02) and stairway aspect ratio ([Formula: see text], 0.2 and 0.3) on the velocity, temperature and local and average Nusselt number profiles are investigated. The results show that by incrementing the Reynolds number and solid volume fraction and decreasing the [Formula: see text]/[Formula: see text] simultaneously, the average Nusselt number increases.