An RRM measuring method of an LTE system in an unlicensed frequency band, a system, a terminal and a base station are provided. The method includes: receiving a downlink signal sent by each base station in at least one base station to determine a busy/idle status of an uplink channel and/or a downlink channel of each base station; calculating a value of RSRQ of each base station, when the uplink channel and/or the downlink channel of each base station is in a busy state or in an idle state; reporting the values of RSRQ to a service base station. The present disclosure measures the values of RSRQ according to the channel statuses of the base station, thus the serving base station determines the service performance of a neighboring base station to select a more appropriate auxiliary cell base station or a target base station when switching.