This study aims to clarify the longitudinal flexural cracking characteristics in hogging moment regions, and propose the practical calculation method of cracking load and ultimate bearing capacity for steel-GFRP strips-UHPC composite deck structure. The longitudinal flexural behavior of two steel-GFRP strips-UHPC composite beams in the hogging moment regions are conducted through a three-point loading test method. Their failure modes and mechanism, cracks propagation and distribution characteristics are analyzed considering the influence of reinforcement ratio. Variation law of mid-span displacement, maximum crack width, strains and interface slip with load are discussed. Calculation method of cracking load and ultimate bending capacity of steel-GFRP strips-UHPC composite beams are proposed. The results show that with the increase of reinforcement ratio, the cracking load, ultimate bending capacity and interface slip value corresponding to the ultimate load are improved effectively. However, the development of cracks is inhibited, the crack width, average crack spacing and strain of reinforcement bars are reduced as the reinforcement ratio increased. The strain distribution along the height of mid-span section satisfies the plane cross-section assumption. Theoretical cracking load and ultimate bearing capacity of composite beams considering the tensile contribution of UHPC achieve good agreement with the experimental values.