通过对抛物线形断面收缩水深的基本方程进行恒等变形 , 得到的无量纲收缩水深是一个典型的一元四次方程式。根据一元四次方程式的解得到抛物线形断面的收缩水深的解析解表达式，为求解抛物线形断面的收缩水深提供了一种新的解法。该解析公式形式简洁、结果准确、适用范围广，克服了目前查图、查表及试算迭代法的缺点。

Through the identical deformation of the basic equation about the contracted water depth of parabolic shaped channel, we can obtain a non dimensional formula, which is a typical quartic equation with one unknown . According to this equation ' s solution, we can also obtain an analytical expression for calculating water depth about the contracted water depth of parabolic  shaped channel, it provides one kind of new solution for calculating the water depth about the contracted section of parabolic shaped channel. The analytical formula is short  cut and its result is correct, and can be widely used. It also overcomes the shortage of consulting graph list and trial computation methods widely used in the past time.