The vibration performance of centrifugal impellers is important for pumps and hydraulic excitation is a key source of vibration. The complex internal secondary flow in the centrifugal impeller brings degradation on vibration performances. An attempt of optimization by controlling the thickness distribution of centrifugal impeller blade is given to repress the internal secondary flow and alleviating vibration. The usual method of modifying an impeller on vibration performance is applying splitter blades. In this study, an ordinarily designed impeller is improved by the optimization attempt and the optimized impeller (OPT) is compared with the prototype impeller (PRT) with traditional splitter blades. The vibration performances of the impellers, the PRT, the ordinary impeller (ODN), and the OPT, are investigated numerically and experimentally. Meanwhile, further study on the influence of the thickness distribution optimization on vibration is conducted. There is a relative velocity gradient from suction side (SS) to pressure side (PS) in impeller ODN, causing nonuniformity of energy distribution. By means of thickness distribution optimization, the impeller blade angle on the PS and SS along the blade-aligned streamwise location is, respectively, modified and therefore the flow field can be reordered. The energy transfer in impeller is also redistributed after the modification of blade thickness distribution. What is more, experimental research upon impeller PRT and impeller OPT is also complemented to support the computational fluid dynamics (CFD) results. The experimental results show that the hydraulic performance of the impellers basically agree with the CFD results and the vibration data also proves a better vibration performance of the OPT.