A random access method, comprising: receiving, by a base station, a preamble sent by user equipment UE (S 201); acquiring, by the base station according to a pre-obtained mapping relationship between first downlink assignment information and a preamble, first downlink assignment information corresponding to the preamble received by the base station, wherein the first downlink assignment information is downlink assignment information used by a random access response message (S 202); and sending, by the base station, the random access response message to the UE according to the first downlink assignment information (S 203), wherein after the sending, by the base station, the random access response message to the UE the method further comprises: receiving, by the base station by using pre-obtained first uplink grant information, an uplink message sent by the UE, wherein the uplink message carries identification information of the UE, and the first uplink grant information is uplink grant information used by the uplink message (S 204); generating, by the base station, a contention resolution message according to the identification information of the UE that is carried in the uplink message (S 205); and sending, by the base station, the contention resolution message to the UE by using pre-obtained second downlink assignment information, wherein the second downlink assignment information is downlink assignment information used by the contention resolution message (S 206). receiving, by a base station, a preamble sent by user equipment UE (S 201); acquiring, by the base station according to a pre-obtained mapping relationship between first downlink assignment information and a preamble, first downlink assignment information corresponding to the preamble received by the base station, wherein the first downlink assignment information is downlink assignment information used by a random access response message (S 202); and sending, by the base station, the random access response message to the UE according to the first downlink assignment information (S 203), wherein after the sending, by the base station, the random access response message to the UE the method further comprises: receiving, by the base station by using pre-obtained first uplink grant information, an uplink message sent by the UE, wherein the uplink message carries identification information of the UE, and the first uplink grant information is uplink grant information used by the uplink message (S 204); generating, by the base station, a contention resolution message according to the identification information of the UE that is carried in the uplink message (S 205); and sending, by the base station, the contention resolution message to the UE by using pre-obtained second downlink assignment information, wherein the second downlink assignment information is downlink assignment information used by the contention resolution message (S 206). receiving, by the base station by using pre-obtained first uplink grant information, an uplink message sent by the UE, wherein the uplink message carries identification information of the UE, and the first uplink grant information is uplink grant information used by the uplink message (S 204); generating, by the base station, a contention resolution message according to the identification information of the UE that is carried in the uplink message (S 205); and sending, by the base station, the contention resolution message to the UE by using pre-obtained second downlink assignment information, wherein the second downlink assignment information is downlink assignment information used by the contention resolution message (S 206).