With the improvement of building insulation requirements, the internal / external insulation technology is developing rapidly. According to the difference of thermal insulation materials, the mortar for internal / external insulation can be divided into several types. When the expanded polystyrene (EPS) board and the extruded polystyrene (XPS) board are used as the thermal insulating materials, it is necessary to use bonding mortar to adhere the boards solidly to the substrate, and finishing mortar also need to be used to protect the surface. If using expanded polystyrene granules, vitrified beads or other fillers as insulation materials, supplemented with cement, gypsum or other binding materials, then it can be used as thermal insulating mortar, usually for surface insulation. There are many requirements on these mortars, such as adhesive strength, shrinkage, crack resistance, weatherability, self weight, etc. Redispersible polymer powder favors the flexibility and adhesive strength of thermal insulating mortar, and cellulose ether can improve its water retention and workability. Additionally, wood fiber / polypropylene fiber can further enhance its crack resistance. By adding air entraining agent, a certain amount of gas is introduced into the slurry, reducing the self weight of the mortar and enhancing its heat preservation.