[Purposes] To apply ultra-high performance concrete with coarse aggregate (UHPC-CA) in engineering structures and significantly reduce construction costs for cast-in-place engineering, a method for estimating its flexural strength is proposed. [Methods] The effects of coarse aggregate content and particle size, as well as steel fiber content, on the mechanical properties of UHPC-CA under different curing conditions were experimentally studied. The statistical relationship between flexural strength and compressive strength was analyzed. [Findings] UHPC-CA with aggregate particle sizes of 5~<8 mm exhibits optimal improvement in workability and mechanical properties. Under standard curing conditions, the compressive strength of UHPC-CA first increases and then decreases with increasing coarse aggregate content, while the flexural strength shows a monotonic decreasing trend. When coarse aggregate content is constant, the compressive strength of UHPC-CA increases monotonically with steel fiber content, while the flexural strength does not increase monotonically. [Conclusions] When steel fiber content is below 1%, the correlation between flexural strength and compressive strength of UHPC-CA is similar to that of ordinary Portland concrete, and the original shape function for flexural strength estimation shows good fitting performance. As steel fiber content increases, the fitting performance of the original shape function gradually deteriorates. When steel fiber content exceeds 1% and coarse aggregate content is below 20%, the correlation between flexural strength and compressive strength of UHPC-CA is fundamentally different from that of ordinary concrete.