Herein, the sea surface environment was simulated and a snapshot hyperspectral camera was used to detect the reflection spectra of spilled oil films with different thicknesses at the sea surface. First, based on hyperspectral images obtained using the snapshot hyperspectral camera, the reflection spectra of oil films were obtained. Hereafter, the wavelet transform was used for analysis, and the Coif5 wavelet base was used as the discrete wavelet transform to obtain the detail coefficient of the 9th layer reconstructed signal to determine the difference in oil film thickness. The oil film thickness and detail coefficient exhibited a good linear relationship, thus enabling accurate identification of the oil film thickness at different locations in a large-scale spilled oil accident. The snapshot hyperspectral detection method used herein significantly improves the spilled oil analysis efficiency and provides references for the rapid detection and real-time monitoring of spilled oil disasters.