Abstract: Marine mussels, as an important marine biological resource, possess diverse bioactive components that show broad application prospects in functional foods, drug development, and biomimetic materials. This review systematically summarizes the research progress on major bioactive substances in mussels, including proteins and bioactive peptides, polysaccharides, and lipids. We systematically describe the specific activities of each component: bioactive peptides are mainly derived from enzymatic hydrolysis of mussel meat, exhibiting multiple functions such as antioxidant, immunomodulatory, antithrombotic, antihypertensive, antibacterial, and osteogenic (promoting osteoblast mineralization) effects. Polysaccharides (mainly sulfated polysaccharides) exhibit antioxidant capacity dependent on sulfate content, along with immunomodulatory, anti-inflammatory, intestinal protective (regulating microbiota, repairing mucosal barrier), antitumor, antithrombotic, anti-aging and neuroprotective, lipid-lowering and metabolic improvement activities. Their uniqueness lies in their dual role in gut microbiota regulation and systemic metabolic regulation. Lipids (ω-3 polyunsaturated fatty acids rich in EPA/DHA) primarily focus on cardiovascular protection and metabolic regulation, supplemented by immunomodulatory, anti-inflammatory, and antioxidant effects. Their advantage lies in reducing triglycerides and low-density lipoprotein, with efficacy superior to plant-derived ω-3. The activities of these three components differ: bioactive peptides stand out in osteogenic and antihypertensive effects; polysaccharides are irreplaceable in anti-aging and intestinal protection; lipids specifically target cardiovascular health. In summary, clarifying the differentiated activities of various mussel components provides a scientific basis for their high-value utilization and precision development.