The invention provides a preparation method of a lightweight thermal-insulation decoration surface material for outer wall, and the method is characterized by comprising the following steps: firstly, adopting ceramic green body waste material, Laiyang soil, sedimentation tank waste material, polished tile waste residue and the like as raw materials respectively at different mass ratios to obtain four types of pellet granules, namely A pellet granule, B pellet granule, C pellet granule and D pellet granule; then uniformly mixing the A pellet granule, the B pellet granule and the C pellet granule according to a mass ratio of A pellet granule to B pellet granule to C pellet granule of 1:2:1, then uniformly distributing the pellet granules in the concavo-convex mold, and paving the surface with a layer of D pellet granule as a base material, obtaining a green body under a pressure of 220 MPa after the process of second material distributing, wherein the mass ratio of the base material D pellet granule to the other three pellet granules is 1-3:10; and sequentially performing the process of drying, jet drawing patterns and sintering so as to obtain the lightweight thermal-insulation decoration surface material for outer wall. Test results show that the lightweight thermal-insulation decoration surface material for outer wall has characteristics of low specific gravity, uniform pore size distribution, low water absorption, high bending strength and low thermal conductivity. The decoration surface material has high wear resistance and enables demonstration of the appearance of stone.