A series of novel hydroxyl-functional hypercrosslinked polymers (named as HCPs-Kae) were fabricated using natural and environmentally benign kaempferol as monomer via one-step Friedel-Crafts reaction. The prepared HCP-Kae1–24 h exhibited large surface area, good hydrophilicity and excellent adsorption performance to 5-nitroimidazoles (5-NDZs). Thus, by applying HCP-Kae1–24 h as a solid-phase extraction adsorbent, a sensitive method was developed for enrichment of 5-NDZs including metronidazole, ronidazole, secnidazole, dimetridazole and ornidazole prior to high performance liquid chromatography analysis. Under the optimum conditions, good linearities were achieved in the range of 0.10–100.0 ng mL⁻¹ for water, 1.3–500.0 ng g⁻¹ for honey, and 1.7–100.0 ng g⁻¹ for fish meat. The detection limits of the method were 0.03–0.05 ng mL⁻¹, 0.4–1.0 ng g⁻¹, 0.5–1.0 ng g⁻¹ for water, honey and fish meat, respectively. High method recovery was obtained in the range of 84–118% with relative standard deviations lower than 8.9%. The established method was successfully applied to the detection of 5-NDZs in environmental water, honey and fish samples. This work provides a new strategy for constructing hydroxyl-functional HCPs by using natural resource as robust adsorbent for adsorption/extraction applications.