The invention relates to a siliceous plastic refractory and a preparation method thereof. According to the technical scheme, the method comprises the steps that under the water bath condition, urea resin, polyacrylamide, carboxymethylcellulose, polyethylene glycol 200 and water are stirred to obtain a binding agent; quartzite, silica powder, silicon carbide and dolomite are mixed and ground till the granularity is not larger than 80 micrometers, under the condition that the pressure is 20-30 MPa, compression molding is performed, thermal treatment is performed at the air atmosphere under the temperature of 1,300-1,450 DEG C, materials obtained after thermal treatment are crushed and screened to obtain a material A with the granularity being 3-4 mm, a material B with the granularity being 1-2 mm, a material C with the granularity being 0.088-0.5 mm and a material D with the granularity being not larger than 80 micrometers; the four materials with the different granularities and silicon nitride powder are mixed to obtain a mixed homogenous material; the binding agent is added into the mixed homogenous material to be mixed to be uniform, and the siliceous plastic refractory is obtained. The siliceous plastic refractory has the advantages of being low in cost and simple in technology, and the obtained siliceous plastic refractory is long in hardening time and large in volume density and strength.