The embodiment of the invention relates to a spectrum forecasting method, device and system. The method comprises the following steps: acquiring first sample data of a target spectrum, wherein, the first sample data comprises the existing service information, channel information and channel state information (CSI) of the target spectrum; extracting the CSI of all the channels for the same service in various time slots from the first sample data so as to generate a sample matrix; extracting spectrum resource occupied mode combination of the target spectrum from the sample matrix; and acquiring second sample data of the target spectrum, matching the spectrum resource occupied mode combination according to the second sample data of the target spectrum, and forecasting the channel state of the target spectrum in the future time slot according to a matching result. By means of the embodiment of the invention, spectrum forecasting can be realized according to the correlation of different channels for the same service, thus lowering the error detection rate and the omission ratio during the spectrum forecasting process and improving the spectrum forecasting accuracy.