The probing system has a sensitivity of 0.48482 pF/m and 0.12072 pF/m, while nonlinearity of 0.078% and 0.36% during axial approach and radial approach, respectively. So it can be concluded that the probing system proposed can be used for ultra precision 3D measurement of small structures with dimension larger than 0.3 mm and depth down to 2.3 mm. The gap between floating plate and fixed plate is a key factor to influence the sensitivity, it can be improved by optimizing MEMS technique, which is our potential work. Besides, some calibration, such as probing force, zero displacement and temperature calibration, as well as uncertainty and coupling experiment are our future work.