To investigate the effects of shear connector types, wet joint, reinforcement ratio, and bonding state in the steel-concrete interface on transverse flexural performance of steel-UHPC (ultra-high-performance concrete) composite deck under hogging moment, eight local full-scale composite decks were tested under static bending, and the parametric study was performed by the finite element method. The test results show that: compared with the specimens using studs, the nominal cracking strength of those using PBL (perfobond leiste) connectors increases by 16.8%. Compared with the integrally cast specimens, the nominal cracking strengths of the specimens with a rectangular-tooth-shaped wet joint decrease by 16%-23%. When the reinforcement ratio in UHPC layer from 1.96% to 2.82%, the nominal cracking strength of the specimens increases by 16.2%. Compared with the specimens with bonded steel-UHPC interface, the initial and nominal cracking strengths of those with the unbonded interface decrease by 10.1% and 5.8%, respectively. The results from the parametric study reveal that: adding perforating rebars in PBLs and decreasing the space of PBLs or studs can effectively improve the post-cracking stiffness of composite decks, and the diameter and space of the hole in PBLs have little effect on the mechanical performance of the composite decks.