The present disclosure discloses a method and a device in a User and a base station used for channel coding. A first node determines a first bit block; performs channel coding; and transmits a first radio signal. Bits in the first bit block are used to generate bits in a second bit block. The bits in the first bit block and in the second bit block are used for an input to the channel coding, an output after the channel coding is used to generate the first radio signal. Channel coding is based on a polar code. A sub-channel occupied by a target first type bit is related to the number of bits in the second bit block related to the target first type bit. The target first type bit belongs to the first bit block. The disclosure can improve decoding performance of polar codes and reduce complexity of decoding.