Abstract: It is studied that the geometry of the differential equations of the fourth order y⁽⁴⁾=f(x, y, y', y", y''') under contact transformations by E.Cartan's method of equivalence.

Key words: The differential equations of the fourth order, contact transformations, Cartan's method of equivalence

摘要： 用E.Cartan的等价方法，研究切触变换下四阶微分方程y⁽⁴⁾=f(x, y, y', y'', y''')的几何。

关键词: 四阶微分方程, 切触变换, Cartan的等价方法