A persistent current switch (PCS) is used for superconducting applications, such as superconducting magnetic energy storage (SMES) system. The authors have proposed a mechanical switch of Y-Ba-Cu-O (YBCO) bulk as a mechanical PCS. In this paper, the authors measured the contact resistance of Ag block with convex curvature and Ag-deposited YBCO sample (dAg/YBCO) in order to study in more depth about the effect of the deposited Ag, contributed greatly for reduction of the residual resistance. As the results of experiments and simulation using FEM, it became clear that it was effective for reducing the residual resistance from a point of increasing the contact area by depositing Ag on contact surface. In addition, it was assumed that the main origin of the residual resistance were the constriction resistance depending on the contact area and the deposited Ag resistance proportional to the layer thickness. Therefore, the thickness of the deposited Ag layer had the optimal value, was 0.60μm in this case. These results may also lead to support to design the mechanical PCS in the future.