Abstract Near-field scanning microwave microscopy (NSMM) has a significant application in the field of semiconductor electronics and two-dimensional materials characterization. Here, this study proposes a two-port vector network measurement method based on the tip-sample model, which is based on the tip-coupling effect, and acquires the microwave S12 parameters by point-by-point scanning to realize the characterization of the spatial microwave field. Under the input power of 10 dBm and sub-micron tip-sample spacing, the method significantly improves the field contrast between the defect region and the surrounding region. In this study, high-resolution detection of the surface defect field distributions with dimensions of 4.7 μm × 2.7 μm and 4.9 μm × 3.7 μm was successfully achieved. The results indicate that the attenuation of the microwave signal caused by the defect regions was 0.49 nW and 0.54 nW, respectively. This method provides a reference nondestructive testing solution for device structures in microelectromechanical systems.