The present invention relates to a polyamide resin composition having substantially improved heat resistance and oxidation resistance. The polyamide resin composition comprises a polyamide copolymer having high heat resistance and high rigidity, glass fiber, citric acid and ethylenediaminetetraacetic acid (EDTA) which can rapidly cause surface oxidation with glass fiber, such that a highly dense oxide film can be formed on a polymer surface at high temperatures for a long time. Accordingly, the polyamide resin composition of the present invention can prevent oxidation and thermal decomposition by exterior oxygen and heat, and have substantially improved physical properties such as impact strength, tensile strength, flexural strength and elongation.