To study nano-modification of composite foam materials based on citrus pericarp by adding different contents of montmorillonite. Four different mass contents (1% , 3% , 5% , 7% ) of nano-materials were added into the composite foam materials based on citrus pericarp residue and starch, respectively. Composite foam materials were prepared using double-screw extruder, and the radius expansion rate, apparent density, compressive strength, moisture absorption rate, scanning electron microscopy and infrared spectrum performance of the composite foam materials were tested. The results showed that addition of 1% and 3% nano-materials enhanced the compressive strength significantly. In addition, a large number of evenly distributed holes were found in the composite foam materials mixed with 3% nano-materials which led to a maximum radius expansion rate and a minimum moisture absorption rate. However, addition of 5% and 7% nano-materials increased the difficulty of extruding in the process. A proper content of nano-materials was the key to increase the foaming effect and the mechanical properties of the composite foam materials based on citrus pericarp residue and starch.