Data compression of interferometric synthetic aperture radar (InSAR) deformation fields significantly enhances the inversion efficiency of coseismic slip distribution models and seismogenic structure parameters. However, traditional compression methods face challenges in balancing the removal of noise/redundant information and the preservation of global/local key deformation features. This study proposes a multifactor quadtree downsampling method constrained by variance, deformation gradient, and coherence for the downsampling processing of the InSAR coseismic deformation field. Significance and coherence coefficients were used to adaptively weigh various factors, and three strong earthquake events with different complexities were selected to verify the effectiveness and robustness of the method. Compared with existing methods, the multifactor quadtree downsampling method maintained balanced sampling rates and lower root mean square error across all cases, and the sampling results improved the resolution of fault slip distributions in three-dimensional slip inversions while reducing model residuals. The results suggest that the proposed method demonstrates low sampling rates, robust performance, effective elimination of low-coherence points, high retention of critical deformation details, and enhanced constraints on the linear distribution of deformation.