The basic properties of defects (self-interstitial and vacancy) in BCC iron under uniaxial tensile strain are investigated with atomic simulation methods.The formation and migration energies of them show different dependences on the directions of uniaxial tensile strain in two different computation boxes.In box-1,the uniaxial tensile strain along the 〈100〉 direction influences the formation and migration energies of the 〈110) dumbbell but slightly affects the migration energy of a single vacancy.In box-2,the uniaxial tensile strain along the 〈111〉 direction influences the formation and migration energies of both vacancy and interstitials.Especially,a 〈110〉 dumbbell has a lower migration energy when its migration direction is the same or close to the strain direction,while along these directions,a vacancy has a higher migration energy.All these results indicate that the uniaxial tensile strain can result in the anisotropic formation and migration energies of simple defects in materials.