The mechanism of high temperature creep associated with the climb of extended dislocations is investigated. Based on the model for the contraction of extended jogs [1], the time needed for the contraction under the action of applied stress and the climb velocity of extended dislocations are derived. And consequently, an expression of the steady state creep rate is obtained. According to this expression, the creep rate is shown to be proportional to the third power of the stacking fault energy. This is consistent with the majority of experimental results. The possible reason for the deviation from the third power relation in some cases is also discussed.