The invention relates to premixed mechanized spraying mortar. The premixed mechanized spraying mortar is characterized by being prepared from, by weight, 60-80 parts of aggregates, 10-15 parts of 42.5 Portland cement, 8-20 parts of fly ash, 1-3 parts of redispersible latex powder, 0.5-2 parts of cellulose ether, 0.1-0.5 part of wood fibers, 0.02-0.05 part of an air entraining agent and 0.05-2 parts of a super lubricant. According to the premixed mechanized spraying mortar, mortar rheology improvement is conducted by adopting machine-made sand taking limestone as mother rock as the aggregates, adopting the cement as a cementing material, adding the fly ash capable of improving the construction performance and doping an additive, and the mortar is not delaminated, not bled, not dispersed and not separated and is good in cohesiveness and extremely little in springback and mortar falling in the spraying construction process.