Biomass carbon has the advantages of affordability, environmental friendliness, and adjustable pore structure. It is a good matrixfor loading transition metals and has broad application prospects in water electrolysis. The specific surface area, pore size distribution, andother physical and chemical structures of carbon carriers directly affect the utilization of transition metal active sites and electrolyte ion diffusion, which is the key to unleashing the potential of transition metal electrolysis for water catalysis and determining catalyst performance.This article introduced the pyrolysis mechanisms of different biomass, summarized common biomass carbon preparation methods such ashigh-temperature pyrolysis, hydrothermal carbonization, and microwave pyrolysis, and compared the advantages and disadvantages of different preparation methods. A summary of targeted control strategies for biomass carbon physicochemical structure, includingphysical, chemical, and template methods, was conducted, and the effects of different control strategies on biomass carbon specific surface area, pore volume, average pore size, and other physicochemical properties were explored. The construction strategies of common biomass carbon-based electrolysis water catalysts, such as doping with heteroatoms and loading with metal active components were summarized. The research status of these catalysts in oxygen evolution reaction, hydrogen evolution reaction, bifunctional catalysis, and hybridelectrolysis of water was also summarized, and the progress made in electrolysis of water was elaborated in detail. And the challenges facedby biomass carbon-based electrolysis water catalysts in controlling micro to mesoporous ratio, improving conductivity, hydrophilicity,and catalyst forming treatment were discussed in the future.