Basic equations of normal and critical water depths for standard-type heteromorphic elliptic section are transcendental which cannot be solved directly. On the basis of summarizing the hydraulic factor calculation formulas of standard-type heteromorphic elliptic section, dimensionless parameters and the method of curve piecewise fitting optimization analysis were introduced to propose the explicit calculation formulas for solving the normal and critical water depth of standard-type heteromorphic elliptic section. The results of error analysis show that the absolute values of relative error of the normal and critical water depth formulas for a typical cross-section were less than 0. 362% and 0. 288%, respectively, which were within the common range in real engineering applications.