Abstract: Time-of-flight secondary ion mass spectrometry（TOF-SIMS）is becoming an important technique for chemical surface analysis since its instrumental performance has been improved. The discovery and application of the cluster ion beams in the past few years promote TOF-SIMS to be used almost as a routine analytical tool for identifying bio-molecules at surface and mapping their 2D distributions at the surface or in the interior of cells and on the cross-section of tissues. The major analytical functions of TOF-SIMS include surface mass spectrometry, chemical mapping and depth profiling. This review(divided into part I and part II) gives brief introduction about how these three analytical functions were applied to solve the problems in biomaterials research and life science during the past two decades. This paper as the first part of the complete review is focused on describing the applications of TOF-SIMS as a surface mass spectrometry to characterize biomedical organic polymer materials surface and common biomolecules including amino acid, peptide, protein, nucleotide, DNA, lipid and sugar at surface. In addition, some examples are given to demonstrate the applications of TOF-SIMS in studying protein adsorption mechanism, chemical surface modification of biomaterials and investigating drug release mechanism of biodegradable polymer.