In order to improve the precision of pure monocular vision for the relative pose between two shields of double shield tunnel boring machine (TBM) during excavating process, this paper presents a new measurement system combining monocular vision and high-precision inclinometer sensors. Two inclinometer sensors are fixed with the camera and feature points separately. By multiple constraints of angles provided by inclinometer sensors and the monocular vision, the pose between front shield and back shield is measured with higher precision. In this paper, simulation shows that the feasibility of the system is validated and it has ideal precision. Afterwards, the experimental platform to simulate the pose of double shield TBM is established, and the accuracy verification experiment is conducted by a total station. The result indicates that the measurement precision is less than 3 mm and much better than that of the pure monocular vision measurement method, which means that this model can satisfy precise measurement requirements of double shield TBM poses during excavating process.