［Objective］ To solve the degradation performance limitations and environmentalconcerns of traditional polyurethane coatings in marine antifouling applications，a series of degradable waterborne polyurethane（WPU）coatings modified with biomass materials were developed.［Methods］ A waterborne polyurethane emulsion with an R-value of 1. 2 was synthesized using polycaprolactonediol and isophorone diisocyanate. The emulsion was then blend-modified with four different biomassmaterials：microcrystalline cellulose（MCC），modified cellulose（MC），coconut shell fiber（CSF），and water-soluble starch（WS）. The polyurethane emulsion was characterized by FT-IR. A systematic evaluation was conducted on the emulsion′s stability，solid content，and the corresponding coating′s pencil hardness，hydrophilicity，and biodegradability. The optimized formulation was combined with anantifouling agent to to prepare antifouling coatings，whose inhibitory efficacy against Chlorella vulgans and Golden-brown algae was investigated. The performance was further validated through field testsusing submerged panels in a marine environment.［Results］Both modified cellulose and water-soluble starch contributed to maintaining the stability of the polyurethane emulsion and reduced the hydrophilicity of the coating. Microcrystalline cellulose，modified cellulose，and coconut shell fiber enhanced the coating hardness. The antifouling coatings exhibited significant inhibitory effects againstboth algal species. Marine exposure tests demonstrated that in the Cu2O system，the addition of 1% microcrystalline cellulose or 1% modified cellulose yielded the best antifouling performance，while in the DCOIT system，1% microcrystalline cellulose was most effective.［Conclusion］Biomass materials can effectively modulate the properties and degradation behavior of polyurethane coatings. The incorporation of 1% microcrystalline cellulose or modified cellulose facilitates effective synchronizationbetween the release of of antifouling agents and the degradation process of the polyurethane matrix， leading to significantly improved antifouling efficacy and showing good application potential.