The invention provides an SAR radio frequency interference (RFI) inhibition method based on inclined projection filtering. The method provided by the technical scheme comprises the following steps: step one, according to SAR receiving echo signals, estimating a direction of arrival of RFI; step two, according to the direction of arrival of the RFI, establishing an RIF subspace and a low-order RFI subspace; step three, by use of the RFI subspace and the low-order RFI subspace, constructing an inclined projection filter; and step four, performing filtering operation on echoes so as to complete RFI inhibition. Compared to a conventional airspace filtering method, the method has the following advantages: the calculation process is not affected by increased errors introduced by space guiding vector correlation under the condition of existence of multiple interference sources, a better interference inhibition effect is realized, and an experiment result provides that the performance is stable.