The present invention discloses a method for determining a subband index, the method comprises: an Evolved Node B (eNB) receives r, calculates a difference between the received r and a formula   〈 N - s i M - i 〉 corresponding to each obtained subband index, searches sequences 〈 N - 1 M - i 〉 , 〈 N - 2 M - i 〉 , … ⁢ , 〈 0 M - i 〉 in a stored intermediate value table according to the calculated difference to obtain each si constituting {si}i=0M−1. The present invention further discloses a device for determining a subband index, the device comprises a table generation module, a receiving module and a calculation module. The method and device disclosed in the present invention are capable of reducing the storage space needed for a subband index report.