The design and preliminary investigation of a real-time, online, all-weather accurate monitoring system for the early detection and warning of difficult-to-detect, inchoate, small-area oil spills were presented. The scheme is based on a miniaturized surface plasmon resonance (SPR) device. The system used a light source with a non-scanning angle modulation to ensure that the light cover the incident angle range of variation related to the samples under test. With a fixed range of sample refractive indices, corresponding to most of the known crude and refined oil products, the parameters for the detector through optimization of the central wavelength and the incident angle of the light source were obtained, as well as related parameters of the prism by a combinational simulation using commercial software packages MATLAB and ZEMAX. Through modeling and simulation, followed by preliminary experiments a basic model for the system feasibility was arrived for the proposed purpose.