 titanium and titanium alloys have become the preferred materials for various medical implants. However, surface modification technology still needs to be strengthened in order to adapt to the complex physiological environment of the human body. Compared with physical or chemical modification methods, biochemical modification, such as the introduction of functional hydrogel coating on implants, can fix biomolecules such as proteins, peptides, polysaccharides, or nucleotides on the surface of the implants so that they can directly participate in biological processes, regulate cell adhesion, proliferation, migration, and differentiation, and improve the biological activity on the surface of the implants. Additionally, this review introduces common substrate materials for hydrogel coatings on implant surfaces, including natural polymers such as collagen, gelatin, chitosan, and alginate, and synthetic materials such as polyvinyl alcohol, polyacrylamide, polyethylene glycol, and polyacrylic acid. Furthermore, the common construction methods of hydrogel coating, electrochemical method, sol-gel method, and layer-by-layer self-assembly. This article was authored by Huang Qinchen, Ray Fong, Tian Xia, and others. We are article.tv. Links in the description below.