The invention provides a method and an apparatus for quantitatively predicting a reservoir forming probability of a fault block oil-gas reservoir. The method comprises the steps of determining main control factors of fault block oil-gas reservoir formation and distribution, wherein the main control factors include a hydrocarbon source kitchen, a phase, a fault zone and a regional cap formation, and the regional cap formation, the phase, the fault zone and the hydrocarbon source kitchen are arranged from top to bottom longitudinally; according to oil-gas control characteristics of the hydrocarbon source kitchen, building an oil-gas control geological model of the hydrocarbon source kitchen, and determining a reservoir forming probability of the fault block oil-gas reservoir under the control of the single factor, namely, the hydrocarbon source kitchen; according to oil-gas control characteristics of the phase, building an oil-gas control geological model of the phase, and determining areservoir forming probability of the fault block oil-gas reservoir under the control of the single factor, namely, the phase; according to oil-gas control characteristics of the fault zone, building an oil-gas control geological model of the fault zone, and determining a reservoir forming probability of the fault block oil-gas reservoir under the control of the single factor, namely, the fault zone; according to oil-gas control characteristics of the regional cap formation, building an oil-gas control geological model of the regional cap formation, and determining a reservoir forming probability of the fault block oil-gas reservoir under the control of the single factor, namely, the regional cap formation; and determining the reservoir forming probability of the fault block oil-gas reservoir.