The invention discloses a polyurethane foamed material based on bagasse and plant oil, and a preparation method and an application thereof. The preparation method of the polyurethane foamed material comprises the following steps: uniformly stirring polyol A and bagasse to obtain a mixed solution I, wherein the polyol A is prepared from plant oil-based polyol and petroleum-based polyol according to a mass ratio of 1:1; and adding water into the mixed solution I, stirring the mixed solution and water, standing the obtained solution, adding isocyanate, stirring the solution and isocyanate, and standing the finally obtained solution to obtain the polyurethane foamed material based on bagasse and plant oil. The method adopting the bagasse as a filler and water as a foaming agent and a catalyst has the advantages of simple reaction conditions and l cost; and the prepared polyurethane foamed material has the advantages of non-toxicity, no pollution and high degradability, and can be widely applied to building heat insulation materials, civil furniture, sound insulation materials, heat insulation materials, and heat insulation interlayer of industrial pipelines and storage tanks.