The invention relates to compound thermal insulation plastering material for external wall, which consists of a compound cementing material and a lightweight aggregate. The compound cementing material consists of cement, active admixture, lime powder, promoter, surfactant, anti-crack and waterproof agent, water retaining agent, flame retardant, re-dispersible emulsion powder, alkali-resistance fiber and coal flying ash cenosphere; the lightweight aggregate consists of EPS grain and expanded perlite. The invention has the advantages of low density, thermal performance, high strength, good impact resistance, bond strength and low shrinkage. The compound cementing material adopts a plurality of polymeric cementing materials, allows the insulation material to have good bond performance and simultaneously ensures falling and slipping resistance performance. The invention has good water resistance and high softening coefficient. By using cement-based cementing material as main material and organic reinforced material and waterproof component as auxiliary materials, the invention has a hydrophobic rate more than 98 percent and a softening coefficient more than 0.7. The invention can save energy and protect environment. A great deal of industrial waste residue is used in the materials, which can save a great number of energy, realize resource utilization of the waste residue and is in favor of environmental protection.