A method and a device in a User Equipment and a base station are provided. The UE receives first information and monitors a first signaling in M Resource Element (RE) sets. The first information determines the M RE sets. The UE assumes that P modulation symbol groups are one-to-one mapped to PRE sets of the M RE sets. One blind detection for the first signaling is performed on the PRE sets. Modulation symbols obtained by modulating the bits in a first bit sequence constitute a first modulation symbol set sequentially. The bits in the first bit sequence are sequentially arranged according to an output of a channel encoder. The first modulation symbol set is successively divided into the P modulation symbol groups, each consisting of X modulation symbols.