Conventional fossil-based foam is difficult to degrade, it therefore raises the problems of environmental pollution and safety issues. Cellulose foam has gradually become a research focus by virtue of its biodegradable natural characteristics. However, the current forming technologies depend heavily on the drying conditions, such as freeze drying and supercritical drying, which are time-consuming and high costly, therefore, the foams production can hardly be scaled up. To solve this problem, a new method of ambient drying to prepare an all-renewable fiber-based foams was investigated. With pulp fiber as the main material, cellulose nanofibrils as the binder in the fiber-based foams network, and the polyvinyl alcohol added as a fiber dispersant and foaming additives, the foam was obtained by thoroughly stirring the fiber solution and drained and dried at ambient temperature. Finally, foam density and porosity were tested, thermal conductivity and mechanical properties were analyzed. It was found that the fiber-based foams prepared exhibited low density in the range of (0.015±0.002)~(0.029±0.004) g/cm3, high porosity (> 98%), low thermal conductivity (The values of the thermal conductivities of fiber-based foams were in the range of ((0.060±0.003) ~ (0.069±0.003) W/(m·K)). The fiber-based foam exhibited a maximum stress of 59.366 kPa at 80% strain, with the value 37.1% higher than that of similar cellulose nanofibrils foam reported. The fiber-based foam could be considered to replace fossil-based foam in the mechanical protection of products from damage and thermal insulation in cold-chain transportation.