本文对利用拉格朗日方程建立平面机构动力学方程的问题，进行了新的探讨和分析．首先对多构件多自由度系统的动能提出了新的表达形式，而后在此基础上推导出了拉格朗日方程平面展开式，并确切地指出了不同情况下，拉格朗日方程展开式中相应各项的数目 In this paper, the use of Lagrange equations to establish a dynamic mechanism of the plane mechanism, conducted a new discussion and analysis. First of all, a new expression of kinetic energy for multi-component and multi-degree-of-freedom system is proposed. Based on this, a plane expansion of Lagrange equation is deduced. It is pointed out that Lagrange’s equation is expansive under different conditions In the corresponding number of items