Abstract: Electron transfer dissociation (ETD), as a novel peptide fragment dissociation technique in mass spectrometric analysis, overcomes the shortcoming of slow electron transferring-rates in electron capture dissociation (ECD), introducing electrons from electron-doner anthracene into reaction system by negative ion chemical ionization resource, and completed electrons transferring stage directly and quickly. ETD retains the labile posttranslational modifications (PTMs) and obtains a complete or almost complete series of ions and thus extensive peptide sequence information. A further benefit is the ability to analyze larger, non-tryptic peptides, allowing for the detection of multiple PTMs and protein top-down strategy.