In the nonlinear dynamic system the chaotic phenomenon can only appear in the autonomous system whose order is higher than three (included), which impels the research work in the nonlinear field to focus on the above-mentioned system. However,very complex dynamic phenomenon may also occur in the second-order autonomous sys- In the nonlinear dynamic system the chaotic phenomenon can only appear in the autonomous system whose order is higher than three (included), which impels the research work in the nonlinear field to focus on the above-mentioned system. However, very complex dynamic phenomenon may also occur in the second-order autonomous sys-