The invention provides a method for determining oil contents in rocks. The method comprises steps of: measuring a plurality of calibration oil samples having different oil contents, and acquiring a holographic fluorescence spectral intensity corresponding to the calibration oil samples; acquiring a fit relation between the holographic fluorescence spectral intensity and the oil contents of the calibration oil, according to the oil contents of the plurality of calibration oil samples and a plurality of three-dimensional fluorescence spectral intensities corresponding thereto; adding a certain amount of the calibration oil after dilution to rocks to be measured, acquiring a sample of the rocks to be measured and performing a holographic fluorescence measurement of the rock sample to be measured; and introducing the holographic fluorescence spectral intensity of the rock sample to be measured to the fit relation, thus an oil content of the rock sample to be measured is obtained. Accordingly, oil is detectable together with an organic solvent without volatilization of the organic solvent, which not only saves time, but also address a low-detection-limit problem for oil content resulting from volatilization of oil when the organic solvent is volatilized in the conventional method.