Optical coherence tomography (OCT) using low-coherence light as the source is an new technique in the field of imaging. By the method of Monte Carlo simulation, the coherent signal under different scattering conditions, the difference between single scattering and multiply scattering and its influence on imaging are discussed. Farther, we outline a method to utilize the difference to enhance the image sharpness and signal intensity. The influence of the incident beam diameter on the imaging resolution is dynamically studied to get a helpful conclusion to the experiment.