The invention discloses a satellite-borne synthetic aperture radar (SAR) imaging method based on Doppler cubic term estimation. The method comprises the following steps of: 1, reading echo simulation data of a satellite-borne SAR sliding beam bunching mode; 2, processing the echo simulation data, and thus obtaining a two-dimensional frequency domain signal; 3, setting a Doppler cubic term initial value, an iteration threshold and an iteration step length; 4, acquiring a signal which is subjected to distance compensation; 5, acquiring an imaging result signal; 6, acquiring the maximum value and position of a one-dimensional signal; 7, acquiring a left first side lobe peak of a one-dimensional signal main lobe; 8, acquiring a right first side lobe peak of the one-dimensional signal main lobe; 9, acquiring an absolute value of difference between the left first side lobe peak and the right first side lobe peak; and 10, comparing the absolute value with a threshold Th, and judging according to a comparison result. The method has the advantages that a high-accuracy Doppler cubic term is obtained by using an iteration method, phase errors brought by the conventional slope distance model under the condition of high resolution are compensated, and a satellite-borne SAR focusing image is obtained, so the effectiveness and accuracy of the method are verified.