This invention provides a spring powered stapler comprising a power spring having a front and a rear end, the rear end of the power spring being limited from moving frontward, a middle section between the front and rear end of the power spring being bent down while the front and rear end of the power spring maintaining in upper positions for storing energy in the power spring, and the front end of the power spring moving rearward as a result of the middle section of the power spring being bent down, and a lock plate, while not moving, holding up the front end of the power spring before the rearward movement of the front end of the power spring exceeding a predetermined distance and releasing the front end of the power spring after the rearward movement of the front end of the power spring exceeding the predetermined distance.