Bio-oil is the only liquid carbon-containing renewable resource, which has to be upgraded before it can be further utilized due to its complex composition, low calorific value, high acidity, high viscosity, etc. Electrochemical upgrading of bio-oil is a novel, mild and easily controllable upgrading method, but it still faces the challenge of coking by bio-oil polymerization , which reduces the quality and yield of upgraded bio-oil. By conducting electrochemical upgrading experiments on modulated bio-oils containing different concentrations of acetic acid and aromatic-rich fraction ( ARF ), and characterizing the solutions and coke after the electrochemical reactions, the effects of acetic acid and ARF on coke yield were studied, and the influence of acetic acid and ARF on bio-oil polymerization coking was discussed. The results showed that acetic acid could inhibit bio-oil polymerization coking. Adding 1% of acetic acid could reduce coke yield by about 25%, and the coke yield could be further reduced as the acetic acid concentration increased. The ARF could promote bio-oil polymerization coking. When the ARF mass concentration increased from 60% to 70%, the coke yield increased by about 70%. When the ARF concentration increased to 80% , the coke yield increased by about 150%. Acetic acid inhibited the self-condensation of phenolic substances in bio-oil, reducing the rate of polymerization coking reaction, while ARF enhanced the hydroxyaldehyde condensation reaction, increasing the rate ofpolymerization coking reaction.