A channel assessment method when a long term evolution, LTE, system operates in an unlicensed band, applied in a terminal, comprising: receiving an uplink scheduling instruction transmitted by a base station in a sub frame n, wherein the uplink scheduling instruction is configured to instruct the terminal to transmit uplink data in a subframe n+i by using an allocated resource; and setting channel assessment time in a subframe after the subframe n and before the subframe n+i, so as to detect a clear or busy state of an uplink channel to be occupied by the terminal, characterized in that the method further comprises one of the following: receiving multiple configuration manners of the starting point of the channel assessment time and identification codes corresponding to the configuration manners, which are transmitted by the base station through the RRC signaling, and receiving a target identification code transmitted by the base station through downlink control information, DCI, signaling, so as to determine the starting point of the channel assessment time according to a configuration manner corresponding to the target identification code; receiving the target identification code transmitted by the base station through the DCI signaling, so as to determine the configuration manner corresponding to the target identification code according to a correspondence between identification codes and the configuration manners of the starting point of the channel assessment time, which is stored in the terminal, and determine the starting point of the channel assessment time according to the configuration manner corresponding to the target identification code; and listening to signaling, for indicating that the subframe ends, transmitted by the base station, so as to determine the starting point of the channel assessment time according to a last subframe of downlink transmission and the number of symbols occupied by the last subframe, which are indicated by the signaling for indicating that the subframe ends. receiving an uplink scheduling instruction transmitted by a base station in a sub frame n, wherein the uplink scheduling instruction is configured to instruct the terminal to transmit uplink data in a subframe n+i by using an allocated resource; and setting channel assessment time in a subframe after the subframe n and before the subframe n+i, so as to detect a clear or busy state of an uplink channel to be occupied by the terminal, characterized in that the method further comprises one of the following: receiving multiple configuration manners of the starting point of the channel assessment time and identification codes corresponding to the configuration manners, which are transmitted by the base station through the RRC signaling, and receiving a target identification code transmitted by the base station through downlink control information, DCI, signaling, so as to determine the starting point of the channel assessment time according to a configuration manner corresponding to the target identification code; receiving the target identification code transmitted by the base station through the DCI signaling, so as to determine the configuration manner corresponding to the target identification code according to a correspondence between identification codes and the configuration manners of the starting point of the channel assessment time, which is stored in the terminal, and determine the starting point of the channel assessment time according to the configuration manner corresponding to the target identification code; and listening to signaling, for indicating that the subframe ends, transmitted by the base station, so as to determine the starting point of the channel assessment time according to a last subframe of downlink transmission and the number of symbols occupied by the last subframe, which are indicated by the signaling for indicating that the subframe ends. receiving multiple configuration manners of the starting point of the channel assessment time and identification codes corresponding to the configuration manners, which are transmitted by the base station through the RRC signaling, and receiving a target identification code transmitted by the base station through downlink control information, DCI, signaling, so as to determine the starting point of the channel assessment time according to a configuration manner corresponding to the target identification code; receiving the target identification code transmitted by the base station through the DCI signaling, so as to determine the configuration manner corresponding to the target identification code according to a correspondence between identification codes and the configuration manners of the starting point of the channel assessment time, which is stored in the terminal, and determine the starting point of the channel assessment time according to the configuration manner corresponding to the target identification code; and listening to signaling, for indicating that the subframe ends, transmitted by the base station, so as to determine the starting point of the channel assessment time according to a last subframe of downlink transmission and the number of symbols occupied by the last subframe, which are indicated by the signaling for indicating that the subframe ends.