Water—insoluble macromolecular particle adsorbents, which were adopt to treat Cd(II) in water, were synthesized at low temperature though the nucleophilic substitution between polyethylene polyamine and cyanuric chloride due to the temperature gradient reaction activity of cyanuric chloride. In this system, the triazine ring of cyanuric chloride served as connection point to combine polyethylene polyamine and cyanuric chloride. The synthesized particulate adsorbent was characterized by elemental analysis, FTIR and SEM. At the same time, the adsorption kinetics, isothermal adsorption model fitting and adsorption mechanism of Cd(II) were studied. The effect of pH on Cd(II) was investigated and the effect of adsorption performance, the performance and structural stability of the adsorption-desorption regeneration cycle of the adsorbent were also studied. The results showed that the adsorption mechanism of the adsorbent was to utilize the coordination complexation of the nitrogen lone pair electrons on the secondary amine on the surface of the particulate adsorbent with the heavy metal ion Cd(II) for adsorption. Which was in line with the pseudo—second—order kinetic equation and the Langmuir adsorption model. The maximum adsorption capacity reached 539.1 mg/g, and the adsorption of Cd(II) was relatively easy, and the adsorption capacity was strong. The initial concentrations of Cd(II) were 3636.5 mg/L and 70.0 mg/L, and the removal rate of Cd(II) can reach 97.5% and 99.9%, respectively, and the adsorption effect remains unchanged during the 10 adsorption—desorption regeneration cycles. The adsorption rate was maintained at about 97.0%~98.2%, the desorption rate was above 97.6%, the recovery rate of the adsorbent was above 92.0%, and the adsorbent can reach 100% recovery after 7 cycles.