In this paper an experimental study of vibration field effect on molded polymers specimens is carried out. A self-made vibration injection device is employed to mold the experiment samples. In the experiment some polyolefin materials are investigated, and property tests for the specimens are carried out. The results show that the tensile strength of high-density polyethylene (HDPE) and polypropylene (PP) have an obvious increase, but polystyrene (PS) does not. The effect of vibration on the strength is related to the temperature, pressure, and gate. Lastly, the test results are analyzed and conclusions are presented. (C) 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1514-1518, 2004.