Polymer hydrogels are a class of materials composed of hydrophilic networks and water, with excellent soft and wet properties. With the development of intelligent materials research, functional polymer hydrogels with light, temperature, and electrical responsiveness have made breakthrough progress. They provide innovative solutions for precision medicine (such as smart drug delivery and tissue engineering), intelligent agriculture (such as water molecule regulation and pollutant adsorption), and the development of interactive pad devices. However, their practical application is still limited by key challenges such as insufficient mechanical strength and low functional integration. However, current hydrogels still face challenges such as poor mechanical properties and single function. This paper reviewed the latest research results of functional hydrogels and discussed the direction of their optimization and multifunctionality, which is expected to provide innovative technological solutions for the fields of precision medicine, environmental protection, and smart materials in the future and promote the rapid development of the related fields.