The invention relates to the technical field of building machinery, in particular to a building slurry dewatering device which comprises a feeding hole (1), a main control box (2), a main controller (3), an insulating layer (4), a drug inlet (5), a moisture inductor (6), stirring blades (7), heaters (8), a first rotary shaft (9), a tank body (10), a first motor (11), a steam outlet (12), a second motor (13), a second rotary shaft (14), a second discharge controller (15), cutter blades (16), a crushing chamber (17), a first discharge hole (18), a first discharge controller (19), a vibration exciter (20), a second discharge hole (21) and a vibration sieve (22); the feeding hole (1) and the drug inlet (5) are formed in the upper end of one side of the tank body (10); and the steam outlet (12) is formed in the upper end of the other side of the tank body (10).