The invention discloses a method and an apparatus for adjusting the spray amount of a desulphurization circulating slurry. The apparatus, which is especially suitable for adjusting the spray amount of a circulating slurry in a wet limestone-gypsum smoke desulphurization system, is an adjusting apparatus which designs an overflow tube of a slurry pool at the bottom of an absorbing tower in a liftable mode, and the spray amount of the slurry can be adjusted by changing the resistance of a spray system of the circulating slurry through adjusting the liquid level of the slurry pool with the adjusting apparatus. The adjusting apparatus comprises an overflow mechanism which comprises movable assemblies (1), straight tubes (2), overflow bend tubes (3), and a connecting tube (8), and a driving mechanism (4), a leading screw (5), guide rails (6), supports (7) and the like which are cooperated by the overflow mechanism. By adopting the adjusting apparatus of the invention, the desulphurization system, which allows the spray amount of the slurry to be adjusted, the power energy consumed by the spray of the circulating slurry to be saved according to the change of the smoke treatment amount, allows energy saving to be realized on condition that the desulphurization efficiency is guaranteed.