Recently, natural fiber becomes an alternative to the synthetic fiber for the composites used in aerospace, automotive, sports, packaging and so on, due to its inherent characteristics like biodegradablity, renewablity, high-specific strength and specific modulus. However, there are still many challenges in the fabrication of the natural fiber composites, including the poor compatibility between the nonpolar matrix and the polar natural fiber, relatively high-moisture absorption and low-thermal resistance of natural fibers, etc. Moreover, when manufacturing this type composite, the processing conditions, fiber loading and inherent properties of fiber not only affect the mechanical properties, but also cause products defects, such as warpage, volume shrinkage and weld lines, which needs a rapid numerical design for the mold and manufacturing parameters. Therefore, the properties of natural fiber composites have been widely investigated to satisfy the increasing demand in different applications. This paper intends to review the mechanical properties, flammability, durability, foaming behaviors and numerical simulation of injection molding process of natural fiber composites.