Abstract: With the advantages of high construction quality, short construction time, lightweight and low cost in the life cycle of the project, many prestressed concrete composite girders with full-depth precast bridge deck panels (PC composite girders) have been widely adopted by precast assembly bridges in practice engineering. Shear connectors are the key parts of PC composite girders, especially for an ultra-high-performance concrete (UHPC)+U shaped bar (Ubar) pocket shear connector, whose shear performances are widely studied at home and abroad. Considering the factors including the number, spacing, anchorage length of Ubar, pin reinforcement, and shear interface form (reserved notch continuous type or reserved hole cluster type) of shear connectors, 10 pairs of shear connector specimens with UHPC+Ubar were made for a push-off test investigation. The effect and rule of the above factors on the shear behavior and shear strength of UHPC+Ubar shear connectors were obtained. The test results show that there are two failure modes, i.e., Ubar breaking and Ubar pulling out from the web occurred in UHPC+Ubar shear connectors with reserved holes or notches. With the increase of the number of Ubar, the initial cracking and ultimate load, cracking, and ultimate stresses of the shear connectors also increase while the reinforcement stresses decrease after Ubar breaking or pulling out. For continuous shear connectors with reserved notches specimens, the ultimate load of the 4Ubar and 6Ubar specimens increased by 93% and 194%, respectively, compared to the 2Ubar specimens. With the increase of the spacing of the Ubar, the ultimate load will decrease. When the spacing between Ubars increases from 100 mm to 150 mm, the normalized ultimate load decreases by 51 kN. Due to the compact arrangement of Ubars in cluster shear connector specimens, the stress is more concentrated, and Ubars play a greater role in ultimate loads, and the cracking load, cracking shear stress, and interface concrete failure shear stress of the cluster shear connector with reserved holes are larger than those of the continuous shear connector with reserved notches. When the anchorage length of the Ubar extending into the UHPC bridge deck is greater than 4 times the diameter, the anchorage length of the Ubar and pin reinforcement have little effect on the ultimate shear strength of the shear connectors. The fitting function of the shear stress-slippage curve of the UHPC+Ubar reserved notch continuous connector and reserved hole cluster connector is established with five characteristic points. Referring to the AASHTO calculation formula and combined with test data, a formula for calculating the shear capacity of UHPC+Ubar shear connectors of PC composite girders is proposed.