The invention discloses a power mechanism for clock comprising dead pulley component 1, spigot shaft component 2, head sheave slice 3, barrel 4, barrel axis 5, front clamping strap 7, rear clamping strap 6 and support saddle 9. The dead pulley component 1 is mounted on the spigot shaft component 2; the barrel 4 is mounted on barrel axis 5; the barrel axis 5 is mounted on the front clamping strap 7 and rear clamping strap 6; the front clamping strap 7 and rear clamping strap 6 are mounted on the support saddle 9, wherein an even-force wheel shaft 11 is mounted between the front clamping strap 7 and the rear clamping strap 6; an even-force wheel 10 with different radiuses on two ends and the head sheave slice 3 are mounted on the even-force wheel shaft 11, wherein a curve on the surface of the even-force wheel 10 is close to a die-away curve of clockwork spring force; and a backstay cable 12 is mounted on the even-force wheel 10 and the barrel 4 and is connected with the clockwork spring of the barrel 4. The power mechanism provided by the present invention has small time error and high accuracy and is at a higher level than a general clock.