Abstract: Cellulose nanofibers (CNF) foam has gained attention in the field of thermal insulation due to its lightweight, biodegradable, renewable nature, and excellent insulation properties. However, CNF foam suffers from drawbacks such as poor mechanical properties, flammability, and limited thermal stability, which restrict their practical applications. This study prepared anisotropic CNF/ANF composite foam by introducing aramid nanofibers (ANF) into nanocellulose fibers, using ice templating method combined with freeze-drying technique. The effects of ANF content and the introduction of anisotropic structure on the microstructure, mechanical properties, thermal stability, and thermal insulation performance of the composite foam were investigated. The results show that,when the mass ratio of CNF to ANF is 2∶1, the CNF/ANF composite foam exhibits an ultra-low density (12.25 mg/cm³), good mechanical strength (axial compressive strength of 74.56 kPa), and excellent thermal insulation performance (25.2 mW/(m·K)). Additionally, this composite foam also possesses good thermal stability and flame retardant properties, which endow it with broad prospects for applications in areas such as insulation and self-extinguishing property.