Abstract: The key parameter to determine whether jadeitite can be named gem grade jadeitite 'jadeite jade' or not is the content (the mass fraction) of jadeite in jadeitite. So far, most methods to determine the mass fraction of mineral in rock are destructive, which is not suitable in gem detection. Based on the changes of mineral composition and mass fraction of mineral in jadeitite, a non-destructive method by measuring the relative density of jadeitite was established in order to get the mass fraction of jadeite. By Static Water Density Method, 186 pieces of jadeitite samples with relative densities of 3.30-3.24 were divided into groups according to different densities. The main mineral composition and mass fraction of minerals in jadeitite were analyzed by X-ray Powder Diffraction, Manual Heavy-sand Analysis, Electron Probe Microanalysis, Infrared Spectrometry and Raman Spectrometry. The linear relationship between the mass fraction of jadeite and the relative density of jadeitite was statisticstically analyzed. Results show that the main minerals in jadeitite are jadeite, albite, and analcite. As the mass fraction (w_A) of jadeite decreases, those of albite and analcime increase, and the measured specific gravities (SG) of jadeitite change accordingly. The relationship between them is w_A=1.3454 SG-3.4531 (r=0.9814), showing a good linear dependence relation. Because the measured specific gravity of jadeitite is approximately equal to the theoretical one, mass fraction of jadeite is obtained by measuring the specific gravity of jadeitite. This non-destructive method applies to jadeitite with a specific gravity of 3.3-3.0, jadeite content of 95%-60%, and sum mass fractions of jadeite and albite of 90%-97%.