Abstract: Magnetic corn cob biochar material was prepared by chemical precipitation method using corn cob as the parent material, and characterized by scanning electron microscopy, transmission electron microscopy, and infrared spectroscopy. The 5.0 mL of environmental water sample was taken, and 150 mg of magnetic corn cob biochar material was added. After vortex for 4 min, a magnet on the outer wall of the bottom of the test tube was placed to adsorb the magnetic corn cob biochar material, and all the upper clear liquid was discarded. Then 1.0 mL of water was added, and the mixture was vortexed for 1 min. The solution was discarded, and 1.0 mL of ethyl acetate (eluant) was added. The mixture was vortexed for 4 min, and the ethyl acetate eluate was collected, and determined by gas chromatography-mass spectrometry. It was shown that the synthesized magnetic corn cob biochar material had a rich pore structure, and approximately spherical Fe₃O₄ particles evenly distributed on the surface of the corn cob biochar. The adsorption process of triazine herbicides conformed to the Langmuir isotherm adsorption model, and its adsorption mechanism was single-layer adsorption, with the maximum theoretical adsorption capacity of 0.604 mg·g⁻¹. Linear relationships between values of the mass concentration and the peak area of 13 triazine herbicides were kept in the ranges of 0.05-10.00 mg·L⁻¹ (altrazinedesethyl, atraton, atrazine, desmetryn, metribuzin, simetryn, ametryn, prometryn, terbutryn, dipropetryn, and cyanazine) and 0.02-10.00 mg·L⁻¹ (terbumeton and hexazinone), with detection limits (3S/N) in the range of 0.01-0.02 mg·L⁻¹. Test for recovery was made according to the standard addition method, giving recoveries in the range of 87.1%-110%, and RSDs (n=6) of the determined values were found in the ranges of 1.8%-5.6% (results for test of intra-day precision) and 2.9%-7.9% (results for test of inter-day precision). The proposed method was used for the analysis of suspected toxic environmental water samples, and prometryn was detected with the detected amount of 5.3 g·L⁻¹.