A random access method, user equipment (UE), a base station, and a random access system, are provided to address relatively long service delay. In various embodiments, after downlink synchronization with a cell is obtained, UE can determine a preamble sequence of the UE in the cell, where the UE has not obtained uplink synchronization with the cell. The UE can then obtain service data and generate a scrambling code, and scramble the service data based on the scrambling code to obtain scrambled service data. The UE can then configure, based on a predetermined resource mapping relationship, time-frequency resources respectively occupied by the preamble sequence and the scrambled service data. The UE then sends on the configured time-frequency resources, the preamble sequence and the scrambled service data to a base station the cell belongs to and receives random access response sent by the base station based on the preamble sequence.