With artificial drilling pits as simulation of corrosion pits of 3 HPB300steel bars, the fatigue crack growth tests on steel bar specimens were conducted based on beach marking method, and FRANC3D was used to analyze the fatigue crack propagation of steel bars. On this base, the crack growth process of 12semi elliptical pits with different sizes was numerically analyzed with different stress amplitudes. The results show that the crack growth rate grows slowly at first, then increases significantly; the fatigue life of the steel bar with larger initial crack depth is notably lowered; the larger the initial crack depth to width ratio is, the shorter the fatigue life of steel bars is; the fatigue life of the rebar decreases with the increase of stress amplitude, and the larger the initial aspect ratio is, the faster the crack propagation rate increases and the shorter the fatigue life is.