Abstract: The stress fields at the top of the penetrating notch in the center of the double-tension-plate are analyzed with 350 sets of sizes by elastic finite element method. The functions of the normal stress concentration factor normal to the length-direction K_t^σ_y, the first stress invariant concentration factor K_t^I₁ and the Mises equivalent stress concentration factor i>K_t^σ are built. The results indicate that all the elastic stress concentration factors increase with the increase of the ratio 2a/W of the length to the width of the notch as the parabolic function, and reduce exponentially with the decrease of the ratio r/a of the radius to half of the width of the notch.