Disclosed are a measuring method, a base station, and a terminal. The method comprises: a base station transmits to a terminal a switching message of a narrow bandwidth receiving mode, thus instructing the terminal to switch to a specified narrow bandwidth to receive information; when channel state information (CSI) of a downlink channel needs to be measured, the base station schedules the terminal to switch sequentially to at least two different measuring narrow bandwidths to measure a downlink reference signal, where the width of the narrow bandwidth and that of the at least two different measuring narrow bandwidths are less than the width of a system bandwidth. The employment of embodiments of the present invention allows the terminal to flexibly switch between the narrow bandwidth and the system bandwidth, reduces power consumption of the terminal, and implements the measurement of the CSI of the downlink channel at the same time.