As an important component of an open shield machine, the digging device plays a decisive role in the working performance of the shield machine. Finite element model is established for the digging device of an open shield machine manufactured by Beijing Sany Heavy Machinery Co., Ltd. by using finite element program. Strength analysis and rigidity analysis are made on the digging device under the bucket digging mode and the extension boom digging mode, and the stress contour and displacement contour of the digging device are obtained, so as to provide reference for the design and optimization of the digging device of open shield machines. Stress test is made on the digging device, and the simulation results and the test results are compared, which verifies the validity of the simulation results. The digging device has been used in the construction of Phase 2 Project of Line 6 of Beijing Metro successfully.