The biomass carbonaceous aerogel (PCA) was prepared through low temperature hydrothermal carbonization，vacu um freezedrying and high temperature carbonization method by using pomelo peel as main raw material.Then two types of electrosorption electrodes，biomass carbonaceous aerogel（PCA） and PCA composited with MnO2（MPCA） were synthesized and their morphology，structure and electrochemical properties were characterized by SEM，XRD，FT-IR，BET and electro chemical workstation.The electroadsorption performance of these two electrodes for Rb+ and Cs+ was investigated.The results showed that the selfmade PCA with three dimensional porous structure that was beneficial to the diffusion of adsorbates.Both the two electrodes have high specific capacitance and good cycle performance.The composition of the electrode had a signifi cant effect on its electrosorption behavior.The addition of MnO2 changed the adsorption selectivity of the ions.Compared with PCA electrode，MPCA ［m（MnO2）∶m（PCA）=4∶1］ electrode adsorbs Rb more than Cs，and the adsorption capacity can reach 85 μmol/g and 64 μmol/g，respectively，with good regeneration performance.