An experimental analysis of the influence of the bumps on the surface forces in micro gap plates is presented. Because of extremely small sizes of micromechanical structures in MEMS, surface forces between micromechanical components may become significant to influence behaviors of microelectromechanical devices. The bumps are important in micro structures as they change the adhesion condition of the plates, and will influence the surface forces in micro gap plates greatly. To identify relative importance of surface forces with bumps, the experimental instrument which consists of the V-shaped electrothermal microactuator, the suspended plate and the flexible beam is designed. The displacements of the suspended plate with different bumps are measured by experiments, and the surface forces are got by calculation. By analysis, it could be found that the surface force increases with the increasing drive voltage and the increasing normal voltage, and the surface force gets the minimum when the number of the bumps is 9.