Surface-enhanced Raman spectroscopy(SERS) has unique advantages such as ultra-high sensitivity, fingerprint information, small samples, and non-destructive detection. The design and preparation of a SERS substrate with excellent reproducibility and stability are key factors in the further development of SERS detection technology. Hydrogel is a new type of encapsulation material; its cross-linked polymer network has a three-dimensional layered structure that can retain a large amount of water and has a good blocking effect on impurities and strong anti-interference ability. Hydrogel SERS substrate has many advantages, such as low cost, high sensitivity, rapid detection, and high throughput. In this review, the research process of SERS substrate, the advantages of hydrogel SERS substrate, and the application of hydrogel SERS substrate in the field of food, biology, and environmental detection are mainly reviewed to provide a new reference for the preparation of hydrogel SERSsubstrate. First, for the SERS substrate research process, early fixed metal nanoparticles(MNPs) rigid solid substrate, precious MNPs tend to oxidate and aggregate. SERS substrate has poor reproducibility, so it cannot analyze the surface rough samples. In the SERS substrate with MNPs modified on the flexible support material, MNPs are easy to separate in the detection process, and the sensitivity and stability of the SERS substrate are poor. The hydrogel is combined with a plasma nanostructure to obtain a SERS substrate with good uniformity and stability. Hydrogel, as the protective layer of MNPs, provides reliable size and charge selectivity for SERS analysis while maintaining high permeability.Furthermore, hydrogel SERS substrate can achieve in situ detection of the target without sample pretreatment, biocompatible composite hydrogels can be directly detected in vivo, and DNA hydrogel substrate can be accurately recognized, hydrogel modified with multiple antibodies allow for the detection of multiple analytes simultaneously, microgel with adjustable mesh size have a selective sieving effect on the target, and 3D nanostructured hydrogel provides more adsorption hotspots. The prepared hydrogel SERS particles, chips-, and patches show great potential for on-site trace analysis in food safety, biomedicine, and environmental monitoring. In conclusion, preparing hydrogel SERS substrates has good development prospects and can provide new references for future analysis and detection fields.