In this paper, different metal-doped carbon aerogels are prepared by one-step carbonization with sodium alginate as raw material. It was known by SEM and TEM that the metal was uniformly dispersed into the carbon aerogels. Cr-doped carbon aerogel has a rich pore structure with a specific surface area of up to 497.4 m² g^-1. The prepared samples were used in the field of supercapacitors, and the test results showed that the Cr-doped carbon aerogel has the highest specific capacitance (312.5 F g^-1).This study not only develops new directions for the utilization of marine biomass resources, but also provides a simple method for preparing metal-doped carbon material.