The invention provides interior wall plastering mortar, which is prepared by mixing the following components in part by weight: 30 to 35 parts of ordinary Portland cement, 4 to 5 parts of hydrated lime, 5 to 10 parts of light aggregate, 50 to 60 parts of heavy aggregate, and 1.0 part of C-type composite auxiliary, wherein the light aggregate is an inorganic vitrified hollow cellular material of which the fineness is lower than 100 meshes; the heavy aggregate is ordinary river sand; and the C-type composite auxiliary is sold by Guangzhou Hecheng Trading Company. The construction method for the interior wall plastering mortar comprises the following steps: diluting the light energy-saving interior wall plastering mortar with water accounting for 30 to 50 percent of the weight of the mortar; and mechanically or manually stirring the diluted mortar until the mortar is mixed uniformly to achieve the viscosity suitable for mechanical spraying or manual construction. Therefore, the mortar can be sprayed mechanically or constructed manually. The interior wall plastering mortar has light weight and energy conservation, can prevent hollowness, cracking and falling off by being matched with a light wall body, can effectively reduce cracking of the mortar, ensures the quality of construction work, has the advantages of heat insulation and noise reduction, low cost of unit area, good grain composition, good peaceability, mechanical construction contribution and simple process.