分别从拉格朗日量、龙格-楞次矢量以及微分方程出发，由万有引力定律导出了开普勒三定律，并积分得到开普勒 方程与轨道周期.利用文献中的数据计算了地球公转轨道的偏心率和周期，发现有的文献给出的地球近日点和远日点速率值 使得计算结果和观测值之间存在较大的不一致.分析其原因并给出了速率的修正值，从而保证了计算结果和观测值之间的自 洽性.

Starting from Lagrangian，Runge -Lenz vector and differential equation，respectively，the Kepler’s three laws are derived from the law of gravity and Kepler' s equation and the orbital period are obtained by integration.The eccentricity and period of revolution of the earth are calculated by employing the data of perihelionand aphelion speed from two references and large inconformity is found between the calculated results and the observed values.The cause is analyzed and the corrected velocities are given resulting in self-consistency.