Temperature-responsive poly(2-hydroxyethyl methacrylate) (PHEMA) and a preparation method thereof are disclosed. In the preparation method, with a system consisting of benzoyl peroxide (BPO) (an oxidant) and 2-methyl-N-[3-(methyl-phenyl-amino)-propyl]-acrylamide (MPAEMA) or 2-methyl-N-[3-(methyl-phenyl-amino)-propyl]-propionamide (MEMA) (a reducing agent monomer) as a redox initiation system, water and toluene as media, a nonionic surfactant as an emulsifier, and 2-hydroxyethyl methacrylate (HEMA) as a polymerization monomer, polymerization is conducted at room temperature and atmospheric pressure to obtain the PHEMA. An alcohol solution of the PHEMA has an upper critical solution temperature (UCST). The method has the advantages of simple and stable polymerization system, low polymerization cost, easy operation, mild conditions, small impact on the environment, and low energy consumption. Moreover, a molecular weight and UCST of a product are controllable within a specified range.