中文摘要：

从应用角度探讨了如何利用数值方法获取两行根数（TLE）。该方法的特点是以差商代替微分，避免了繁琐的偏导数求解。结果表明，该算法简洁明了，运算速度快，适用于要求实时性的应用。

英文摘要：

SGP4 is an orbit prediction software based on the analytic theory, its input data is two-line elements （TLE） specially defined NORAD. In order to get TLE, a numerical method is discussed, especially on displacing the differential coefficients with numerical differences. The results show that the method is effective.