In recent years, marine oil spill has become an important disaster for marine environment. Marine oil spill quantity is an important indicator for evaluating the threat of oil spill. This paper focuses on the Doppler spectrum of one-dimensional (1D) nonlinear ocean covered by oil film. Oil film damps the capillary wave of the ocean, which leads to a smooth profile of the ocean covered by the film. The paper is devoted to the detailed analysis of the electromagnetic magnetic wave scattering from a sea that is covered with oil. More precisely, it focuses on the case of homogeneous oil slicks. This allows better detection of oil spills, as well as possibly an estimation of the amount of oil spilled, as the scattering coefficient depends on the layer thickness. The 1D Creamer nonlinear ocean is proposed based on the PM spectra. The Marangoni damping effect is considered for modeling the contaminated rough ocean surface. First, the influence of oil film on the ocean surface spectrum and geometrical structure are examined briefly in the present study. On this basis, the influence of oil film on the Doppler spectrum signature (in L-band) of the backscattered echo of the clean and contaminated rough ocean are studied in detail based on the iterative physical optics. The results of the Doppler spectrum signature including Doppler shift and spectral bandwidth of the backscattered echo from Creamer nonlinear ocean surface are different from those of the linear ocean surface especially at the big and moderate incident angles, which shows that it is necessary to adopt the Creamer nonlinear model in the paper. The simulation results show that the Doppler spectrum signatures including Doppler shift and spectral bandwidth of the echo from ocean covered by oil film are significantly affected by sea slicks. The influence of some important parameters, such as wind speed, oil-damping values and incident angles on Doppler spectrum signature is investigated and discussed in detail. Moreover, simulation results indicate that the Doppler spectrum signature is a promising technique for the remote sensing of oil films floating on sea surfaces.