The invention discloses a preparation method for a foam ceramic thermal insulation building block. The preparation method includes the steps that water is added into a uniformly mixed foam ceramic blank, stirring and aging are performed, and the aged blank is laid and piled on a porous refractory support plate; then the aged blank laid and piled on the porous refractory support plate is pressed by using a special forming die into a porous blank body, wherein the forming die is composed of a bottom die with a punching needle and a porous pressing plate, after pressing is finished, the bottom die and the porous pressing plate are separated, and the porous blank body together with the porous refractory support plate are taken out; drying is performed until the water content is less than 2%, heating is performed to 1050-1200 DEG C in a high temperature furnace at a heating rate of 3-5 DEG C/ min, heat insulation is conducted for 0.5-1.5h, and a foaming agent is decomposed to form pores; and furnace cooling is conducted, and cutting is performed to obtain the foam ceramic building block. The porous blank body structure designed by the invention accelerates the gas penetration and discharge, promotes oxidative decomposition of minerals in the blank body, so as to achieve rapid firing of large volume foam ceramic products, and effectively reduce the temperature difference between inside and outside, and solve the cracking problem of large volume thick foam ceramic due to cooling.