The invention discloses a method for effectively acquiring event-related magnetic field information in magnetoencephalogram signals. The method includes the steps of firstly, collecting and preprocessing magnetoencephalogram data; secondly, building a time-frequency atom database; thirdly, using a single-channel matching pursuit algorithm to build a linear combination; fourthly, forming a multi-channel matching pursuit algorithm; fifthly, determining iteration termination by the total residual energy of all channels so as to obtain atoms after signal decomposition; sixthly, removing the atoms representing artifact noise, and rebuilding the signals. The method has the advantages that the magnetoencephalogram signals are post-processed by the method, stimulation times can be reduced greatly, and test results are prevented from being affected by the fatigue, which is caused by long-time and repeated stimulation, of a scanned person; the training amount of a to-be-tested person is reduced, the requirements of the to-be-tested person are lowered, and the selection range of to-be-tested persons of clinical researches is expanded; data collecting time is reduced, research cost is lowered, and the clinical actual researches and popularization and application of event-related magnetic fields are benefited.