Abstarct: In this study, numerical simulation of forced convective heat transfer over a heated square cylinder in a horizontal channel with adiabatic walls has been investigated by the lattice Boltzmann method (LBM), then the square cylinder rotate 45˚ and the variation of the frequency and amplitude of the pulsating flow are studied. A new model was used to calculate thermal and flow fields in curved boundaries. The simulation was carried out with a fluid with Pr = 0.71 and the Reynolds number was fixed at 160. The result have been presented in the form of streamlines, instantaneous drag and lift coefficient around the cylinder, vorticity and temperature contours, local Nusselt number, periodic-surface average Nusselt number. A high accuracy was observed by comparing results of the present study to other numerical. Result shows when the square obstacle rotate 45˚, the mean time average drag coefficient increases but the rate of heat transfer decrease. increase in the amplitude and frequency leads to increase in the value of the periodic-surface average Nusselt number.