Abstract: An analytical force formula of a particle exerting on a slowly moving wall of a one-dimensional infinite square-well potential is obtained. This result is extended into the situation of many non-interacting Fermi particles. At absolute zero temperature，the coherent part in the force is mainly contributed by the eigenstates with the highest energy level and its higher next one.

Key words: one-dimensional infinite square-well potential')"> one-dimensional infinite square-well potential, force formula, coherent effect, Fermi particles