In the chaos range of Lorenz equation, there is interaction between the smaller and larger scales. On the one hand, the Rayleigh number r determines the convective and turbulent flows in the air. On the other hand, the convective and turbulent flows have a feedback to the larger scale condition. The result of interaction between the scales leads to the decrease of the value of r, until the steady state of Lorenz equations is established. During the feedback process, the variation in vertical thermal flux xy and vertical temperature gradient z are the main causes that decide the change of number r. Moreover the end result of feedback displays a abrupt change.