Abstract: In this paper, starting from the horizontal atmospheric motion equations approximate on the equatorial beta-plane, the characteristics of stability, bifurcation and catastrophe of large-scale horizontal motion in the low-latitude atmosphere is studied under some simplified conditions. The analytical solutions and flow patterns of the motion are also discussed in some particular cases. Furthermore, the result derived is then used to analyze and discuss the general features of the active/break phase and oscillation of monsoon. A number of significant conclusions are obtained.