Abstract: Concerning the noise of spectral-domain optical coherence tomography, a method of interference spectrum decoupling was proposed. The method achieves image denoising by eliminating DC and auto-correlation noise of interference spectrum. The white-light source was used for the imaging experiment of the polystyrene single-layer film. The one-dimensional depth image and the two-dimension cross-sectional image of a single-layer film were obtained. The inner micro-structure and the surface topography of the film can be clearly seen from the image. It was experimentally demonstrated that this method can eliminate the image noise effectively, and improve the signal-to-noise ratio and contrast of the image.