Photothermal optical coherence tomography (PT-OCT) imaging technology is applied to the three-dimensional imaging of tumor tissues. An algorithm, which uses the cross-correlation to extract the signal and calculates average amplitude for solving optical path difference imaging, is proposed to suppress noise and enhance image contrast. The agar sample and the mouse ear model are imaged successively in the validation experiment. Compared with the ordinary OCT and the PT-OCT based on the phase difference algorithm, the proposed method can be used for the mouse ear imaging with more details of capillaries, and the enhancement of the imaging effect of tomographic image can be obtained. In the experiment of imaging tumor model, the three-dimensional (3D) PT-OCT images are acquired from the excised tissues which are observed from different angles and different cut surfaces by the proposed method and the corresponding imaging range is 4 mm×4 mm×3 mm. The distribution of capillaries can be clearly identified. PT-OCT has the advantages of convenient, rapid, non-invasive, high-resolution, and 3D imaging, making it more applicable in clinical diagnosis and treatment of tumors.