To elucidate the molecular mechanism of kelp polysaccharides metabolism by Microbulbifer sp. ALW1 with kelpdegrading ability, this study investigated its proteome during kelp polysaccharide metabolism. Two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) were utilized to identify the differential proteins involved in the metabolism of three kelp polysaccharides (laminarin, fucoidan, and pectin) by the ALW1 strain. 2-DE results revealed 202 differentially expressed protein spots, and 161 proteins were finally identified using MS. Cluster analysis showed that 35, 88, and 68 intracellular proteins were upregulated when cultured with laminarin, fucoidan, and pectin as a carbon source, respectively. GO analysis showed that the differentially expressed proteins were mainly concentrated in cell and cell part in terms of cellular component, catalytic activity and binding function in terms of molecular function, and cellular process and metabolic process in terms of biological process. The proteomic study on the metabolism of different kelp polysaccharides by Microbulbifer sp. ALW1 lays a theoretical foundation for the molecular mechanism of polysaccharide metabolism and production of low-molecular-weight kelp polysaccharides and oligosaccharides using this strain.