The mechanical properties of polymer films are of great significance for their optimal design， preparation and application， but existing methods generally find it difficult to effectively measure their thickness direction. To this end， this paper proposed a method for characterizing the full-field mechanical properties of films using phase contrast optical coherence tomography. Leveraging the high sensitivity of PC-OCT imaging for full-field displacement， combined with a film stretching and compression loading device， this method achieved full-field tomographic strain measurement in the thickness direction of sub-millimeter films. Furthermore， by integrating principles of elasticity mechanics， the elastic modulus and Poisson's ratio of the material could be calculated from the full-field strain results. By constructing a film tomographic mechanical measurement system based on PC-OCT， the system was first used to quantitatively characterize a single-layer silicone rubber film with a thickness of 0.6 mm under compression and tension loading， yielding an elastic modulus of 2.461 MPa and a Poisson's ratio of 0.470. Subsequently， a three-layer film made of silicone rubber and glass adhesive was subjected to full-field measurements under compression and tension loading， revealing mechanical differences of each layer in the depth direction. The elastic modulus of the glass adhesive film was measured to be 1.005 MPa， with a Poisson's ratio of 0.450. The method described in this paper can measure the full-field strain and local stress in the thickness direction of micro-deformed sub-millimeter films， thereby determining the mechanical parameters of elastic modulus and Poisson's ratio. This enables highly sensitive testing of the mechanical properties in the thickness direction of the films， representing a novel and effective approach for studying the mechanical performance of thin film materials.