针对高中数学中普遍存在的涉及二次曲线上动点的距离极值问题,本文从理论基础、思维实践和方法特色三个方面论述运用“二次曲线及其相交情形的退化”处理动点距离最值问题,使方法系统化,理论与思维实践紧密融合,让高中数学教师体会到运用通法解决问题时,比通常所谓“巧解”、“特解”更简洁流畅,更具有数学美. Aiming at the problem of the extremum of distance involving upper point of the quadratic curve in high school mathematics, this paper discusses the use of the “degeneration” of the “quadratic curve and its intersection case” from three aspects: theoretical basis, thinking practice and methodological features Point distance from the value of the problem, the method of systematic, theoretical and thinking practice closely integrated, so that senior high school math teachers understand the use of common law to solve the problem, than the usual so-called “clever solution”, “special solution ” more concise and fluent , More mathematical beauty.