The invention provides a method and a system for monitoring deformation of a two-dimensional surface based on microwave interference. The method for monitoring the deformation comprises the followingsteps of S1, selecting stable reference points and target to-be-monitored points; S2, solving the deformation amount of each point; S3, compensating the error; S4, solving the horizontal displacementand vertical displacement; S5, monitoring the deformation. The system for monitoring the deformation comprises at least two microwave interference deformation measuring radars, n stable reference points, a plurality of target to-be-monitored points, a radar control system and a remote monitoring platform, wherein n is greater than or equal to 2; the radar control system comprises an error compensation module, a displacement calculation module and a deformation monitoring module. The system has the advantages that the system is suitable for monitoring the deformation of edge slops and dams; theinstallation is simple and convenient, the use cost is low, the automation degree and accuracy are high, the monitoring effect is good, the easiness by interference is avoided, and the deformation can be stably monitored by measuring the deformation components of the two-dimensional surface in the horizontal and vertical directions.