The invention discloses an imaging method by a large squint angle airborne SAR spotlight mode based on non-uniform sampling. Based on an analysis of azimuth signals characteristics of targets at different azimuths on the same range gate under the condition of a large squint angle, the method enlarges the azimuth imaging range output by effective focuses by a non-uniform interpolation resampling processing method. In the method, a data acquisition model under the large squint angle is equated with a right side looking data acquisition model of increment motion compensation. The method comprises the following steps: firstly, performing cubic phase compensation in an original data field, then performing range walk correction on a time domain and range migration correction on a 2D frequency domain, completing azimuth compression by the non-uniform interpolation resampling method, and finally, completing autofocus processing by a phase gradient autofocus algorithm. Compared with the prior art, the method can help process a larger squint angle, and has the advantages of small calculation amount and easy real-time processing. The method can be applicable to the conventional radar systemswithout a function of tracing Dechirp demodulation by a scene center.