Abstract: In order to ascertain the optimal molding thickness of knitted reinforced thermoplastic composites made from commingled yarns,equation for calculating its theoretical molding thickness is derived,which is expressed by the following factors:linear density and volume density of the reinforcing fibers and the thermoplastic mattress fibers respectively,pliers of the two single fibers in the commingled yarns,and total density of loops and loop length of the prefabricated knitted fabric made from commingled yarns.And the relationship between the theoretical molding thickness and the optimal molding thickness was decided through experiments,providing a reference for preparation of knitted reinforced composites.