This study analyzed the Cassie state to Wenzel state transition of droplets on surfaces decorated with assemblies of cylindrical pillars arranged on a silicon wafer from the point of view of energy.The relation curve between energy barrier of state transition on the cylindrical array of different parameters and droplet size was calculated.For droplets size larger than 2 μl，two methods could be used for the transition from Cassie state to Wenzel state: increasing the droplets’ gravitational energy or maintaining constant droplets’ size and increasing the cylindrical array spacing distance.The experimental results were consistent with theoretical analysis.