Fluid pressure in spatial domain was solved by means of finite element method,and the distribution of fluid pressure was analyzed for different gaps in the straight-wall and the flange in hydro-mechanical deep drawing(HDD).Based on the distribution of fluid pressure in the flange,the minimum blank holding force was given in HDD.A method to select the gap and determine the minimum blank holding force was presented.The condition of the uniform pressure below the die corner was discussed.The results indicate that the gap ratio bet ween the straight-wall and the flange determines the distribution of fluid pressure.Larger the gap ratio will result in more homogeneous distribution of fluid pressure in the straight-wall and the die corner.