The invention discloses masonry 
mortar used in an 
underwater alkaline environment. The masonry 
mortar comprises the following components, according to a weight ratio, 180-220 parts by weight of 
Portland cement, 30-50 parts by weight of special 
cement, 705-715 parts by weight of natural medium sand, 13-18 parts by weight of resin glue 
powder, and 30-40 parts by weight of a special additive. The special additive is mixed from 2-5 parts by weight of a 
thickening agent, 0.5-1 part by weight of a super-
plasticizer, 5-8 parts by weight of a thixotropic agent, 12-15 parts by weight of an adjusting admixture, and 5-8 parts by weight of an early strength agent. The masonry 
mortar is adjusted by high-performance additives special for 
underwater masonry mortar, and resin materials good in alkaline resistance are added, so that the masonry mortar is prevented from undergoing a reaction in the alkaline condition, and hardening and mortar performance aren't affected. At last, the masonry mortar is not prone to disperse, good in construction, resistant to alkaline, normal in 
underwater hardening, and high in strength in a working condition with water.