As a dispatchable resource, biomass energy plays a significant role in the rational resource scheduling and cooperative planning and operation of rural energy systems by participating in the interactive competition of energy markets. Against this background, a multi-agent collaborative planning method for rural energy systems considering biomass trading is proposed. First, a framework for multi-agent collaborative planning in rural energy systems is established. The seasonal characteristics of agricultural biomass in rural areas are analyzed, and models for biomass availability and gas production in biogas station are constructed. Then, according to the interests and trading modes of different stakeholders, objective functions and constraint models are formulated for rural integrated energy system operators and pumped storage power station operators. The Nash bargaining theory is used to solve the collaborative planning model, determining the energy system planning scheme and trading mechanism. Finally, a case study using data from a rural area in Guangxi is conducted to verify the effectiveness of the proposed method through simulation. Results show that the proposed method can stimulate the initiative of each agent, fully dispatch biomass resources, and achieve cooperated planning and operation among multiple stakeholders within the rural energy system, effectively safeguarding the interests of all parties.