The calibrating method for an electrochemical probe, neglecting the effect of the normal velocity on the mass transport, can cause large errors when applied to the measurement of wall shear rates in thin wavy flow with large amplitude waves. An extended calibrating method is developed to consider the contributions of the normal velocity. The turbulence-induced normal velocity component is included into the 2-D mass transport equation by means of its root mean square value multiplied by a random function. The wave-induced normal velocity component is postulated to be proportional to the normal interfacial velocity in thin wavy flow. The inclusion of the turbulence-induced normal velocity term is found to have a negligible effect on the mass transfer coefficient. The contribution of the wave-induced normal velocity can be classified on the dimensionless parameter, V. If V is above a critical value of V, $V_{crit}$, the effects of the wave-induced normal velocity become larger with an increase in V. While its effects negligible for $V
