The partial wetting at nano/microstructured surfaces can be described using the intermediate wetting state between the Cassie-Baxter and Wenzel state. However, the limitation of partial wetting model is still unclear. In this study, surface free energy analysis at the microstructured Si-water interface was performed from both theoretical and experimental aspects to verify the partial wetting model. The effective wetting area was estimated by electrochemical impedance spectroscopy method for the further analysis of the surface free energy experimentally. The partial wetting model was verified at the fabricated microstructured surfaces with its geometrical parameters smaller than 400 μm.