In order to develop a low-cost, fast, and efficient adsorbent, the fish bone charcoal B prepared at 600 °C was modified by chitosan (Cs) and FeO to produce the material Cs-FeO-B. Results showed that Cs-FeO-B had magnetic responsiveness and can achieve solid-liquid separation, macropores disappeared, pore volume and specific surface area are increased, and amino functional groups appear on the surface. The adsorption process of Cd(II) by Cs-FeO-B conformed best to the pseudo-second order kinetics model and the Langmuir model, respectively. The behavior over a whole range of adsorption was consistent with chemical adsorption being the rate-controlling step, which is a very fast adsorption process, and the isothermal adsorption is mainly monolayer adsorption, which belongs to favorable adsorption. In addition, the saturated adsorption capacity obtained for the Cs-FeO-B to Cd(II) was 64.31 mg·g, which was 1.7 times than B. The structure and morphology of Cs-FeO-B were characterized through SEM-EDS, TEM, FTIR, and XRD, indicating that the main mechanism of Cs-FeO-B and Cd(II) is mainly the complexation of amino groups, and it also includes part of the ion exchange between Cd(II) and FeO. Therefore, Cs-FeO-B can be employed as an effective agent for remediation of Cd contaminated water.