The invention provides a water-free water-soluble powdery casting coating and a preparation method thereof. The water-free water-soluble powder casting coating comprises the following components of arefractory aggregate, a suspending agent, a binding agent and other additives, wherein the components comprises the following mass ratio that 100 parts of the refractory aggregate, 3-5 parts of the suspending agent, 0.5-1.5 parts of the binding agent and 2.5-5 parts of the other additives. The preparation method comprises the following steps that during preparation, bentonite and sepiolite are mixed with water at a ratio of 1 to 1 under stirring, the bentonite and the sepiolite are completely dispersed uniformly, stood for a period of time, dried in a microwave drying kiln, dehydrated and thengrinded; the other components are mixed according to the ratio and then ball-milled by a ball mill; then pre-treatment material of the suspending agent is added, so that the material of all the components are uniformly dispersed; and finally, baking and dehydrating are carried out in a microwave drying kiln, and packaging is carried out by using a plastic packaging bag with a sealing property andthe like. The coating has the advantages of being convenient to use, stable in suspension property, free of deterioration after being stored for a long time, environment-friendly, pollution-free, andconvenient to transport.