The invention discloses a predicting method and apparatus for production capacity of a single well in a karst oil-gas reservoir. The method comprises the steps of acquiring three-dimension earthquake files concerning a karst oil gas area, dividing the karst oil gas area into a plurality of geological units, taking the geological units as research units and extracting M geological parameters of various sampling wells, selecting N geological parameters that are mostly relevant to early period production capacity from the M geological parameters to serve as preferred geological parameters, building a correlation between the early period production capacity and the property of an important storing layer, setting a linear relationship between the preferred geological parameters and the important storing layer, building a non-linear relation equation between early period production data and the preferred geological parameters, using the Marquardt's algorithm to determine the undetermined coefficients of the non-linear relation equation so as to determine the non-linear relation equation, and predicting the production capacity of all sampling wells based on the non-linear relation equation and the preferred geological parameter values.