This article describes an original sequence tag search algorithm developed at the Institute for Analytical Instrumentation, RAS. This algorithm is intended for solving the tasks of protein and/or peptide analysis by means of mass spectrometry. It is one of the fundamental bioinformatic algorithms for mass spectrometry data analysis and interpretation. Initial testing of the algorithm has shown  good quality of peptide fragment mass spectrum recognition. The algorithm is of a universal nature and can be applied both to instruments developed by IAI and third-party mass spectrometers, especially MS/MS tandems.