The present disclosure provides a method and device in a node for wireless communications. A first node transmits a first sequence and a first radio signal, the first sequence is associated with the first radio signal; and receives a second radio signal; the first radio signal is used to carry a target identifier; the second radio signal comprises a first information block, the first information block comprises a first field and a second field, the second field is used to determine a first value, and the first value is a non-negative integer; the first field and a value interval to which the first value belongs are used to determine whether the second radio signal comprises a second information block. Through the re-analyzing of the existing signalings, the present disclosure avoids extra signaling overhead, realizes contention resolution of 2-step RACH, and supports flexible switching between 2-step RACH and 4-step RACH.