Embodiments of the present invention disclose a measurement method, including: acquiring, by user equipment, a status of using a target unlicensed frequency band by a target radio access technology RAT; and selecting, by the user equipment, a corresponding measurement mode according to the usage status to measure a radio condition of the target unlicensed frequency band. The embodiments of the present invention further disclose user equipment, a network device, and a system. In the present invention, the user equipment can accurately measure the radio condition of the unlicensed frequency band, so as to provide reference information for the network device to schedule the user equipment.