The invention discloses a preparation method of a one-step sintered glass-ceramic composite board. The preparation method comprises the following steps of A, carrying out impact molding on a green body; B, glazing and printing, namely after drying the green body obtained in the step A, cleaning the surface of the green body, spraying a ground coat, and printing in a way of inkjet printing, roller printing, silk screen printing or a combination of several selected from all the ways, wherein the ground coat contains 3-5% of pyrophyllite; C, applying glass-ceramic frits, namely spreading the glass-ceramic frits on the surface of the green body obtained in the step B, and spraying a layer of polyurethane fixing agent, wherein the polyurethane fixing agent is prepared from the following components in percentage by mass: 3.8-4.8% of nonionic polyurethane associative thickener, 1.8-2.4% of attapulgite clay, 0.6-1% of defoaming agent, 0.6-1.6% of dispersing agent and the balance of solvent; D, sintering, namely sintering in a kiln at the temperature of 1150-1250 DEG C; and E, polishing to obtain a finished product of the glass-ceramic composite board. By using the method, adverse effects caused by the adsorption effect of a preheating zone of the kiln to the glass-ceramic frits can be avoided, and the rate of finished products can be increased.