Abstract: The downward motion of materials within the post-flare loop of February 18,1984 under the joint action of solar gravity and the both gravity and the both gradients of the magnetic field pressure and atmospheric pressure is studied. Thevelocity distribution along the loop is calculated in the case that the temperaturechanges within the loop but the shape of the loop changes less with time. The results obtained show that the downward motion at both the top and the middle ofthe loop can be regarded as free d.ownward motion due to solar gravity, but atthe bottom of the loop, the motion is obviously affeCted by material density andthe magnetic field strength within the loop.