The phase transformation in cavitation flow field was calculated by the full cavitation model considering the pressure and velocity turbulent fluctuation of the fluid, as well as the influence of noncondensable gas based on the homogeneous flow assumption. The turbulence viscosity coefficient was modified by the density function. A computation model and calculation method was proposed for the steady cavitation. The steady cavitation flow field of ALE15 hydrofoil was numerical simulated for the cavitation numbers of 2.3 by using the computation model and calculation method according to the conditions in the experiment. The calculated velocity distributions on different profiles agreed well with the experiment data, which validated the reliability of this computation model and calculation method. The velocity far away from the hydrofoil section was close to the velocity in the main flow region, and gradually decreased along the flow direction for the reason that the cavity acted as an obstacle. There is a large vortex zone in the cavity rear, and the velocity near the hydrofoil section is negative, both caused by the re-entrant jet. 