Ultra high performance concrete (UHPC) has been widely used in bridge engineering with its high strength and high durability. In precast UHPC segmental beams, the shear characteristics of shear keys have become a common concern due to the lack of corresponding specifications. Therefore, by using the finite element software ABAQUS, the direct shear performance of UHPC can be simulated, with three main research parameters included: shear area, lateral stress and joint type. An analysis and comparison have been made of the failure modes and load displacement curves of components under different working conditions, thus obtaining the influence rules of each parameter on the performance of UHPC components. The analysis shows that with the increase of the shear plane area, the shear capacity of the member is significantly improved; as the lateral stress, which is small, not higher than 0.3fc, increases, the failure load of the component increases approximately linearly. Due to the good overall performance of the rubber joint component, the shear bearing capacity is 16%, which is higher than that of the dry joint component under the same conditions. The calculated values of the JSCE specification in Japan are in good agreement with the numerical simulation test results, which shows that the design formula of the Japanese JSCE specification shear key can predict the shear capacity of UHPC joints.