A method of processing spectrum monitoring (SM) big data based on tensor decomposition comprises the steps of: S1: processing calibration of geolocation V, synchronized clock t, synchronized time tn(0 . . . N); of SM stations and determining SM sampling point M and bandwidth B; S2: processing discretization for a monitoring time and structured processing of SM data for a monitoring period to obtain a one-dimensional SM sequence Itn at the given sampling time and a two-dimensional SM matrix W at the given monitoring period; S3: constructing a cuboid matrix Q based on the two-dimensional SM matrix W, processing tensor decomposition for the cuboid matrix Q and identify the emitter.