Outer wall facing mortar as well as preparation method and application thereof

The invention relates to the technical field of mortar, and particularly discloses exterior wall facing mortar as well as a preparation method and application thereof. The raw materials of the mortar comprise cement, rubber powder, gypsum, auxiliaries and filler, the auxiliaries comprise a water repellent and an anti-cracking agent, the filler comprises graded sand and ball-milled modified perlite, the weight of the ball-milled modified perlite accounts for 0.5-3% of the total weight of the filler, and the components of the ball-milled modified perlite comprise fly ash, bentonite and perlite powder. The ball-milled modified perlite is uniformly distributed in the mortar, can adsorb and convert a part of calcium hydroxide in the mortar into calcium silicate gel, can effectively fill gaps in the mortar, and reduces the possibility that free alkali is brought to the surface of a plaster layer by water to form efflorescence under the assistance of the anti-cracking agent and the water repellent; therefore, the in