Twisted-Wire Pair(TWP) is commonly used in the comprehensive wiring of electronics and information equipment. In high frequency electromagnetic environment, TWP may couple with external electromagnetic fields, which would interfere or destroy the connected equipment. In order to research the TWP’s electromagnetic pulse effect, based on transmission line theory, the calculation expressions of TWP response to external electromagnetic pulse are deduced. Results show that in high frequency electromagnetic environment, the TWP has stronger anti-electromagnetic interference ability. The research method and conclusion in this paper may be helpful to the quantification research of TWP’s electromagnetic pulse effect and the anti-electromagnetic interference ability assessment.