The invention provides a method and apparatus for determining an entrapment geological resource amount. The method comprises: an entrapment effective volume and a unit reserve factor are obtained; and according to the entrapment effective volume and the unit reserve factor, calculation is carried out to obtain an entrapment geological resource amount being a product of the entrapment effective volume and the unit reserve factor. According to the method provided by the invention, the entrapment geological resource amount can be calculated only by obtaining the ntrapment effective volume and the unit reserve factor, so that a defect of a large calculation result offset caused by inaccurate obtaining of an entrapment geological resource amount calculation parameter can be overcome. Therefore, a solid foundation is laid for objective and reasonable estimation of the entrapment geological resource amount and exploitation plan formulation and exploitation investment decision making can be carried out conveniently.