Here, we describe a simple one-pot solvothermal method for synthesizing MIL-101(Fe)@polydopamine@Fe O composites from polydopamine-modified Fe O particles. The composite was used as a magnetic adsorbent to rapidly extract sulfonylurea herbicides. The herbicides were then analyzed by high-performance liquid chromatography. The best possible extraction efficiencies were achieved by optimizing the most important extraction parameters, including desorption conditions, extraction time, adsorbent dose, salt concentration, and the pH of the solution. Good linearity was found (correlation coefficients >0.9991) over the herbicide concentration range 1-150 μg/L using the optimal conditions. The limits of detection (the concentrations giving signal/noise ratios of 3) were low, at 0.12-0.34 μg/L, and repeatability was good (the relative standard deviations were <4.8%, n = 6). The method was used successfully to determine four sulfonylurea herbicides in environmental water and vegetable samples, giving satisfactory recoveries of 87.1-108.9%. The extraction efficiency achieved using MIL-101(Fe)@polydopamine@Fe O was compared with the extraction efficiencies achieved using other magnetic composites (polydopamine@Fe O , Hong Kong University of Science and Technology (HKUST)-1@polydopamine@Fe O , and MIL-100(Fe)@polydopamine@Fe O ). The results showed that the magnetic MIL-101(Fe)@polydopamine@Fe O composites have great potential for the extraction of trace sulfonylurea herbicides from various sample types.