The invention discloses a tension spring mouse killer which comprises a killing device and a double-lever secondary pressure-reduction trap device, wherein the killing device comprises a mouse killing part and related parts such as a gate, plate nails, a movable bar, a tension spring, handle levers, a machine pin, a left column, a right column, a base, an upper panel and a limit pin; the double-lever secondary trap device comprises a lever body A, a lever body B, an A lever pin, an A lever power point hook, an A lever resistance sheet, a B lever power pin, a B lever resistance pin, a B lever pin, a safety lever, a step lever and a rubber-covered wire shaft seat; the A lever resistance sheet blocks the machine pin, the A lever power point hook just hooks the B lever resistance pin, and the step lever is upwards pulled and attached to the B lever power pin, so that the trap device is formed; and when a mouse collides the step lever, the movable bar and the gate at the front end of the movable bar smash downwards fiercely, and the plate nails kill the mouse instantly. With the adoption of the killing device and the double-lever secondary trap device, the tension spring mouse killer has the characteristics of high sensitivity, good effect, non-pollution, durability and low cost.