Kinetic modeling of large-scale metabolic network require a generic enzymatic rate equation. In the generic form, kinetic parameters are clear and precise enough to correlate to experimental data and construct a database. Such a uniform form is easy to deal with arbitrary number of substrates and products in computation of dynamic modeling. The generic rate equation is symmetrical in both directions of reversible reaction and formally exact under the quasi-steady state condition. Here presented the rigorous derivation of generic rate equation from further three classical enzymatic rate equations and discussed the characters and uses of the generic form.