Abstract: In order to investigate the flexural behavior of concrete beam reinforced with 400 MPa fine grain high steel bars, the static bending tests on four rectangle cross-section concrete beams were made.Mechanical characteristics, flexural capacity of normal section, crack and deflection were analyzed according to present code.The results show that the flexural behavior of concrete beam reinforced with 400 MPa fine grain high steel bars is similar to normal concrete beam, the average concrete strain of different height keeps plane;flexural capacity and crack spacing could still be calculated by the current code for their values are close to the tested values.The current code was not suit able for calculating crack width;deflection value calculated by current code was a little smaller than the test value, so the stiffness-calculating formula was proposed to multiply 0.85 for adjustment;under the state of serviceability, crack width and deflection meet the requirements of the current code.