Biomass carbon aerogels have attracted increasing interest worldwide for capacitive deionization (CDI) desalination due to their hierarchical pore structure distribution, high specific surface area and modifiability. Herein, carboxymethyl cellulose (CMC) is used as a raw material, and Zn2+, Fe3+, and Al3+ are used as crosslinking agents to prepare carbon aerogels through "sol-gel, freeze-drying, high-temperature pyrolysis." A CMC//AC asymmetric CDI electrode device is constructed for desalination. The results showed that coordination involving metal ions and carboxyl groups formed a carbon aerogel with a three-dimensional network structure; moreover, the addition of metal ions significantly increased the surface charge and graphitization of the material. Among the systems studied, CMC-Fe showed abundant pseudocapacitance due to redox reactions of the Fe. Gasification of Zn further increased the pore volume (2.11 cm3 g-1), specific surface area (1844 m2 g-1) and total specific capacitance (365 F g-1) of CMC-Zn. Al exhibited no obviously favorable behavior. Additionally, the prepared CMC-Zn showed good cycling stability, and the capacitance remained at 98% after 100 charging and discharging cycles. The CMC-Zn carbon aerogel electrode achieved a significantly high adsorption capacity of 25.8 mg g-1, showing that it has great potential among carbon materials for desalination.