We study non-distorted imaging depths of optical coherence tomography (OCT) system in different tooth tissues based on Monte Carlo modeling of tooth OCT imaging. Two-dimensional simulated OCT images of single tooth enamel, dentin and two-layer tooth tissues are obtained by simulating the incident Gaussian beam and light propagation in dental tissues. The simulated images exhibit qualitative agreement with the experimental ones. The average non-distorted imaging depths of three kinds of dental tissue structure are gained through the analysis of one-dimension OCT signals corresponding to the simulated OCT images. It is indicated that the non-distorted imaging depths of the OCT system in dental tissues are 150~2400 μm, the non-distorted imaging depth of the enamel is much greater than that of the dentin. The results have certain reference value for the judgment on effective tissue structure information in experimental OCT images.