Aiming at the oil leakage problem of the joint of hard pipelines in wind tunnel hydraulic system, the finite element model of oil pipe with SAE split flange connection was established in Abaqus, the influence rules of O-ring seal pre-compression rate, working oil pressure, radial deviation and angular deviation before tubing assembly on flange connection sealing were analyzed.The results show that O-ring has self-sealing character, and the sealing performance is enhanced with the increase of pre-compression rate, the contact stress on sealing surface increases with the increase of working oil pressure,the radial deviation and angle deviation in tubing installation result in uneven distribution of contact stress and even local yield phenomenon, but the assembly deviation has little influence on the static sealing performance of sealing ring within a certain range; when the radial deviation of oil pipe per 100 mm is greater than 1.2 mm and the angel deviation is greater than 5°, the flange seal fails quickly.