The invention discloses recycled wet-mixed mortar and a preparation method thereof. The recycled wet-mixed mortar is prepared from the components in parts by weight as follows: 180-260 parts of cement, 130-240 parts of limestone flour slurry with the moisture content being 30%-60%, 380-650 parts of recycled fine aggregate, 650-900 parts of natural medium sand, 2.7-3.9 parts of a water-retention thickener, 0-3.0 parts of a setting time regulator and 120-210 parts of water. The recycled fine aggregate produced with waste concrete test cubes through crushing is applied to wet-mixed mortar, a technical method of pre-stirring of the recycled fine aggregate and stone powder slurry as well as utilization of a special additive is used, the problems of high water absorptivity of the recycled fine aggregate, and quick workability loss, reduced strength and the like are solved; not only is the problem of treatment of waste concrete test cubes solved, but also higher economic benefit is produced.