Under quasi-steady-state conditions, the general current equations of the chronoamperometry and cyclic voltammetry at disk and hemispherical microelectrodes were derived by solving the partical differential equations. A quantitative meaning of quasi-steady-state or steady-state process for chronoamperometry at disk or hemispherical microelectrode is given and examplified. Many experiments are carried out to verify the validity of the results. The methods for the determination of heterogeneous rate constant and charge transfer coefficient are also developed.