Porous carbon materials, utilized as electrodes in capacitive deionization (CDI), play an important role in water desalination. Currently, benefiting from the abundance, cheap, environmental-friendly, biomass converted carbon was selected as the carbon electrode. We study the salt adsorption properties of carbon materials prepared by biomass precursor such as wood, eggplant, etc. The as obtained biomass converted carbon was further processed with activation. Potassium hydroxide, as a chemical activation agent, was selected and reacted with biomass converted carbon at high temperature. The influence of activating agent-carbon ratio and activating temperature was investigated. Due to the natural porous morphology, the biomass converted carbon materials usually exhibit a large surface area and high electrical specific capacitance after carbonization. Taking advantage of these properties, biomass converted carbon materials own a good water desalination performance. Additionally, the salt adsorption property of activated biomass converted carbon usually has an obvious enhancement, which benefit from the creation of extra porous structure. Based on our experiment, the activated biomass converted carbon materials are excellent candidates to be utilized in further industrial water purification.