A molding resin composition comprising 99.9 to 50% by weight of polyimide represented by the formula: ##STR1## and 0.1 to 50% by weight of polyether ketone resin and/or polyester resin, and more particularly comprising the polyester resin capable of forming an anisotropical molten phase at a temperature of 420.degree. C. or less, and a polyimide-based molding resin composition which comprises the said resins and other additives such as phenolic resin, fluororesin, graphite, carbon fibers, aromatic polyamide fibers, potassium titanate fibers and a crystallization accelerator, and is excellent in thermal resistance, chemical resistance, mechanical strength and processability.