The invention discloses a construction method for preventing efflorescence at corners of a building wall. The construction method comprises the following steps that preparation before construction isconducted; the building wall is constructed, specifically, a foundation and a wall frame of the building wall are constructed; a dry hanging structure is designed, specifically, a red brick layer, a hanging piece, a force-bearing piece and a sound absorption layer are sequentially arranged on the wall frame from outside to inside; the red brick layer is pasted, specifically, before red bricks aremounted, anti-alkali treatment agents are smeared on the back faces and side faces of the red bricks, meanwhile, resin glue is smeared at the bottoms of the red bricks, and then chemical fiber mesh cloths are pasted to form an anti-pull waterproof layer; whitewashing is conducted, specifically, putty whitewashing is conducted on the outer side of the mounted red brick layer; and prevention treatment is conducted, specifically, the whitewashed wall is washed through 10% of an oxalic acid solution and washed through fresh water after being washed completely, and after being fully dried, the wallis sprayed through a solidification waterproof agent. The construction method starts from the three aspects of design preparation before construction, reducing of generation of substances such as Ca(OH) 2 and salt, and prevention treatment after construction, and generation of the efflorescence phenomenon at the corners of the building wall is lowered.