Abstract: The use of some stable isotope regents has limitations due to relative high price and synthesis difficulties; as a result, we developed a new method for quantitative proteomics research by using metal element chelated tags (MECT) coupled with mass spectrometry. The principle of the method lies that the bicyclic anhydride diethylenetriamine N, N, N’, N’’, N’’-pentaacetic is covalently coupled to the primary amines of peptides, and then chelated to rare metal Y and Tb. After peptide modifications, the tagged peptides are mixed and analyzed by LC-ESI-MS/MS. The MECT method was evaluated by using standard proteins as model samples. The experimental results showed that metal-chelate-tagged peptides chromatographically coeluted successfully during the reversed-phase LC analysis. The relative quantitation results were accurate for proteins using MECT. Bicyclic anhydride diethylenetriamine-N, N, N’, N’’, N’’-pentaacetic modified N-terminal of peptides could promote cleaner fragmentation (only y-series ions) and improve the confidence level of protein identification. The MECT strategy provides a simple, rapid and economical alternative to current mass tagging technologies available.