The development of industry has caused a large number of dyes to be discharged into water bodies, causing serious pollution to the water environment and harming the entire ecosystem. Therefore, it is important to develop portable and rapid detection technology. Surface-enhanced Raman spectroscopy has the advantages of high single-molecule level detection sensitivity, short detection cycle, and molecular fingerprint specificity. Its application in the field of water organic dye detection has received widespread attention, but this technology relies on reliable substrates with high enhancement and high signal reproducibility, but the synthesis of substrates mostly uses toxic and hazardous materials, posing potential environmental risks. The use of non-toxic chemicals, non-polluting solvents and renewable materials are important considerations in green synthesis strategies. In summary, this paper adopts a hydrothermal method to green synthesize nano-silver and use it in surface-enhanced Raman technology to detect organic dyes in water. First, a simple, fast, and green synthesis method was adopted, using sodium alginate as the reducing agent and stabilizer, and water as the reaction medium. The nano-silver hydrosol was prepared by hydrothermal reduction of silver nitrate, and a reliable substrate for this experiment was obtained. The structure and surface morphology of nano-silver were analyzed by UV-visible spectrophotometry and transmission electron microscopy. The results showed that the prepared nano-silver hydrosol had a large particle size, a wide distribution, a good dispersion and a spherical shape, and an average particle diameter 46 nm. Three dyes (methylene blue, rhodamine B, and basic fuchsin) were formulated into solutions of different concentration gradients and then mixed with the prepared silver gum for surface-enhanced Raman detection. The Raman spectrum of the dye solution was detected, and the characteristic peaks were identified by reference to the literature. Raman characteristic peak can be detected when the concentration of the pure solution is 1×10^-3 mol·L^-1. However, there was no characteristic peak at 1×10^-4 mol·L^-1 concentration or lower. The detection of the Raman spectra of the silver gum showed that there was no Raman peak, indicating that the silver gum had no background effect on the Raman spectra of the mixture. The Raman spectral characteristic peak position of the silver gum mixture is still relatively obvious at low concentration gradients. These results show that the Nano-silver synthesized by this method has a good Raman enhancement effect on the three dyes, and the sensitivity can reach 10^-6 mol·L^-1. With the emphasis on environmental protection, the surface-enhanced Raman technology using Nano-silver synthesized by green method as a reliable substrate will have a broader application prospect in the field of dye wastewater detection.