This study conducts seven full-size cantilever beams specimens using high-strength reinforced steel bars (f_y = 685 MPa, f_(yt) = 785 MPa). In addition, the investigation and analysis of twenty - two simple-supported beams and three cantilever beams. The specified compressive strength of concrete is 70 and 100 MPa. The purpose of this study is to investigate the flexural crack development of high-strength reinforced concrete beams (HSRC). The experimental data is used to verify the application of the flexural crack control formulas described in Foreign specification and related researches on HSRC beam members. The study concludes the design formulas for the flexural crack based on ACI 318-14, which contains the reinforcement spacing (s) and the thickness of the concrete protective layer (Cc) of the restrictions. Satisfying the restrictions can control the crack width at 0.4 mm under the service-level loading.