The invention relates to the field of preparation of insulation boards, and discloses a preparation method of a high-strength compound cement-based insulation board. The method comprises the following steps: A) Portland cement, coal ash, diatomite, shell powder, hollow glass beads, sepiolite, organic and inorganic compound heat storage particles, bagasse fiber and mineral wool fiber are uniformly stirred, and a solid component is prepared; B) carboxymethyl cellulose, sodium alginate, and sodium dodecyl benzene sulfonate are added into water with uniformly stirring, and a liquid component is prepared; C) the solid component and the liquid component are mixed and heated with stirring, and cast slurry is prepared; D) the cast slurry is cast into a die, moulding and solidification, demoulding, maintenance and drying are carried out, and a finished product is prepared. A cement foaming agent is used, and the prepared insulation board has the advantages of light weight, good uniformity of hole dimension and distribution, good insulation effects, and high strength.