Abstract: In order to study the pullout performance of a new type of steel-UHPC composite dowel connector, based on the steel dowel connector of a single-box double-cell steel box of UHPC bridge deck of Wanjiali Ramp Bridge in Changsha City, and on the basis of accurately reflecting the vertical shear resistance of the connection parts of the steel-concrete composite box girder, two groups of 16 composite dowel connectors (steel dowel-stud and steel dowel) were designed and manufactured, and pull-out tests were carried out. The formula for calculating the ultimate pull-out capacity of a single steel dowel and multiple steel dowel in UHPC was proposed by the grounds of ABAQUS finite element numerical simulation and on theoretical formula derivation analysis. The results showed that the initial failure modes of the composite dowel connectors were UHPC ductile failure, including shear failure and axial tensile failure. The stiffness and bearing capacity of steel dowel-stud connectors were higher than those of steel dowel ones. After adding studs, the pull-out bearing capacity of the specimen could be increased by about 47% ~ 85%. The ultimate pull-out bearing capacity of the new composite dowel connector could be increased by increasing the effective embedding depth of the steel dowel, the tensile strength of UHPC and the supporting volume. Based on the Concrete capacity design (CCD) model theory, the calculation formula for the pull-out anchorage capacity of the tenon-type composite dowel was derived. Comparing the theoretical calculation value and the experimental value of the pull-out bearing capacity of the tenon-type composite dowel, the two were in a good agreement.