The oil fluorescence was measured by laser induced fluorescence (LIF) along with enhanced light excitation. The saturation effects in oil fluorescence spectroscopy were studied on two aspects, namely, the fluorescence intensity and spectral offset. In the experiment, it was shown that the intensity of fluorescence becomes to worse when the intensity of excitation pulse raises. The characteristics of fluorescence intensity at 430 nm in the linear and nonlinear ranges were derived through polynomial nonlinear curve fitting. Furthermore, the three-dimensional oil fluorescence spectra based on the excitation light energy were reconstructed according to the nonlinear fitting data derived from the fluorescence intensity in the detection wavelengths. The result demonstrated that the offset of oil fluorescence spectral peak and the nonlinear characteristics of the spectrum intensity with saturated excitation can be used to identify the oil samples which can not be distinguished by the general fluorescence spectroscopy.