Abstract: In gem identification and research, relative density is an important parameter of gem physical properties.It is commonly measured by hydrostatic weighing method, which takes a few steps thus taking longer measuring time.Therefore it is not preferred in laboratory batch measurement.In the paper, the authors developed a new relative density measurement method, based on an improved formula of hydrostatic weighing method, so that the desired measurement can be done in a simplified way by using a computer.One can more quickly and accurately measure the relative density value according to the new method.In this paper, we compared the new method with hydrostatic weighing method and the data showed both results were consistent and the new method yielded reliable data.