Embodiments of the present disclosure relate to the communications field, and provide a method for predetermining a resource in random access, user equipment, and a base station, so that a process of random access can be simplified, and reliability of information transmission in the process of random access can be improved. The method is: an implicit manner is used to indicate some or all of identifiers of a random access preamble index; so that a message in a procedure of random access is simplified, and at the same time resources used for transmitting an RAR reply message, transmitting a contention resolution message, retransmitting an RAR reply message, and retransmitting a contention resolution message are configured by using signaling or preset by a system. The embodiments of the present disclosure are used for a process of random access.