In order to investigate the mechanical properties of the inflatable antenna reflectors under low temperatures， uniaxial tensile tests of Kapton （polyimide） foils are conducted. Kapton foils with a thickness of 2μm are used and the strip specimens are manufactured according to the machine direction （MD） and the transverse direction （TD） of the foils. The stress-strain curves of the foils are obtained under five temperature conditions （20℃， 0℃， -10℃， -40℃， -70℃） after uniaxial tensile tests. The changing mechanism from nonlinear to linear about tensile curve with the temperature decline is explained. Based on the above curves， the temperature coefficient of Kapton foils is proposed and afterward tensile strength， elongation at break， equivalent yielding stress， yielding strain and elastic modulus are analyzed and calculated. By analyzing the above mechanical parameters， the fitting formulas with temperature coefficient as the variable are given. Above all， the tests results provide basis for partial coefficients of Kapton foils strength design value in low temperature， and meanwhile provide basic material data for the extreme temperature field effect test in orbit for the inflatable antenna structure in the future.