The invention discloses a method for treating joints of thin plastered heat-insulation composite plates, and relates to the technical field of heat-insulation decorative plates. The method includes steps of 1, carrying out pre-processing; 2, carrying out plate adhering, to be more specific, selecting the thin plastered heat-insulation composite plates in corresponding shapes with corresponding sizes, smearing bonding mortar on the back surfaces of the thin plastered heat-insulation composite plates, adhering the thin plastered heat-insulation composite plates on base-layer walls and reservingdecorative plate gaps between the thin plastered heat-insulation composite plates; 3, carrying out plate gap filling, to be more specific, filling the decorative plate gaps with foam strips after thebonding mortar on the back surfaces of the thin plastered heat-insulation composite plates is completely dried, reserving caulked joints between the thin plastered heat-insulation composite plates andfoam plates and adhering adhesive tapes on decorative surfaces of the thin plastered heat-insulation composite plates around the caulked joints; 4, treating the caulked joints, to be more specific, treating the caulked joints by the aid of sealant and tearing off the adhesive tapes after the sealant is applied; 5, cleaning plate surfaces; 6, carrying out acceptance inspection. The method has theadvantages that excellent air conditions can be assuredly maintained in construction environments, good aesthetics can be kept, at least 20% of joint treatment cost can be saved, and site constructionprocesses can be accelerated.