The invention discloses a micro-foaming masterbatch and a preparation method thereof and a foaming plate of a refrigerator. The micro-foaming masterbatch comprises coating resin, and sodium hydrogen carbonate, azodimethyl phthalamide, citric acid, an activator and a nucleating agent dispersed in the coating resin, wherein the weight ratio of sodium hydrogen carbonate, azodimethyl phthalamide and citric acid is (25-50) to (50-70) to (25-50). According to the technical scheme, by compounding a heat-absorbing inorganic foaming agent sodium hydrogen carbonate and citric acid and an exothermal organic foaming agent azodimethyl phthalamide in a proper portion, heat absorbed and released in a foaming agent decomposing reaction process is balanced as soon as possible, so that the stability of melt viscosity of raw materials is guaranteed when the foaming agent is decomposed, and therefore, the foamed pores are more uniform and stable, and meanwhile have greater foaming porosity. By adopting the micro-foaming masterbatch to foam and extruding and forming the micro-foaming material, the insulating effect of the micro-foaming masterbatch is enhanced, the surface effect is good, and the micro-foaming masterbatch the advantages of being small in pore diameter, uniform in pore distribution and light in weight.