Hydrogel have three-dimensional structure which is hydrogel is simply a hydrophilic polymeric network cross-linked in some fashion to form generate an elastic structure. Injectable hydrogel is technique in which active substance and biomaterials is injected into body fluid formation of situ soild hydrogel. Active substance such as drugs, Protein, genes, virus Injectable hydrogel are developed by photo cross linking polymerization by two types chemical and physical cross linking. Injectable hydrogel improve some properties such as good biocompatible, good biodegradable, controlled drugs release ability. Injectable hydrogel is injected into body fluid and formation of situ solid hydrogel.