The waveguide-type evanescent wave sensor depends on the interaction between the analyte and the evanescent field, and its detectability is determined by the intensity of evanescent wave. However, the intensity of evanescent waves in waveguides is relatively low compared to the amount of light that propagating in the waveguide core. As a result, the sensitivity of sensors is greatly limited. In this paper, we propose a waveguide probe based on hydrogel polymer to overcome this issue. The three-dimensional network structure of the hydrogel facilitates the penetration of the analyte into the waveguide, allowing the transmitted light localized inside the waveguide to be used for detection. This significantly improves the utilization efficiency of the transmission light. In addition, the experiment successfully suppressed the additional optical losses caused by water-induced swelling deformation of the hydrogel waveguide by adding other polymer monomers. Since the waveguide prepared from pure hydrogel causes deformation upon water absorption and swelling, which brings additional light loss, other polymers in addition to hydrogel are doped to maintain the basic shape of the waveguide. The experiment results show that the hydrogel polymer waveguide sensor has an absorption detection limit of is 1.0×10^-9 g/mL for rhodamine B aqueous solution and 1.0×10^-19 g/mL for fluorescence, which is about 7 orders of magnitude higher than that of other waveguide-based evanescent wave sensors. The hydrogel polymer waveguide sensor has the advantages of simple preparation, low cost, high adaptability and excellent sensitivity making it a promising candidate for various, applications, such as medical treatment and environmental monitoring.