The invention discloses a method for calculating underground reservoir regulation storage capacity. The method is used for calculating the regulation storage capacity of a non-dam and non-closed underground water storage space (an underground reservoir). The method is used for underground water recharge areas, overall consideration is given to natural conditions such as hydrogeological conditions, water storage media, boundary conditions and infiltration (precipitation or rivers or lakes or reservoirs) and human factors such as artificial exploitation and recharge, an underground water three-dimensional geologic model and a numerical simulation model serve as a basis, and the boundary conditions and mining scale are controlled, so that a multi-year adjustable underground reservoir capacity calculation method which ensures that water can be injected into, stored in and exploited from the underground reservoir is provided. The method has the advantages that calculation is convenient and applicability is high.