Abstract: Considering the characteristic of the GEO SAR (geosynchronous synthetic aperture radar), a new slant range model without the "stop-go" assumption was established. Meanwhile, an advanced ωk algorithm overcoming the 2-D space-variant was proposed for GEO SAR, this algorithm adopted a new frequency axis mapping and NUFFT in both range and azimuth direction to decrease the 2-D coupling. Finally, effectiveness of the algorithm was validated by the simulations.