To investigate the shear performance and the calculation methods for shear capacity of prestressed ultra-high performance concrete (UHPC) I-shaped beams, a total of three prestressed UHPC I-shaped beam specimens were designed and tested under one-point loading. Critical experimental results including the load-deflection relationship curves, failure modes, and crack patterns were obtained. Based on the test results, French UHPC code, Swiss UHPC code, specification of highway bridges in China and application specification draft of ultra-high performance concrete for highway bridge and culvert, the shear capacity of the test specimens were calculated and their feasibility were discussed. Additionally, the modified compression filed theory (MCFT) was adopted to calculate the shear capacity of the test beams based on Mohr-Coulomb and Rankine criterions. It was found that the shear capacity of UHPC beams decreases with the shear span-to-depth increases and the stirrups have a great impact on the shear capacity. The results show that the calculation of various specifications is relatively conservative. The calculation results of the Mohr-Coulomb criterion are closer to the experimental values than those of the Rankine criterion. Because the test beam with a small shear-span ratio is in a bending and shearing state, the Mohr-Coulomb criterion can consider the influence of normal and tangential stresses on the compression zone, where the simulation results are closer to the actual condition.