Abstract: A polyamide 6,6 resin composition having improved toughness, abrasion resistance and frictional resistance is provided herein. The polyamide 6,6 resin composition comprises a graft copolymer of polyethylene and maleic anhydride, layered nanoclay, and a nucleating agent with a predetermined composition ratio in a base resin of polyamide 6,6 having ultra high viscosity. The polyamide 6,6 resin composition has properties of tensile strength (ISO527) of 83 Mpa or greater, elongation at break (ISO527) of 30% or greater, a kinematic friction coefficient of steel to metal measured by a ring-on-ring friction and abrasion tester of 0.30 or less, and a specific abrasion amount of 0.020 mm3/Kgf·km or less. The resin composition is useful as a worm gear for a motor-driven power steering device.