The Gezhouba ship lock has been suspended for repairs due to multiple damages to the bottom water seal device of the miter gate，resulting in a long suspension time and causing huge losses to the Yangtze River shipping.The reason for the damage to the bottom water seal is analyzed.It is proposed to change the active segment of the sealing device into a fixed segment.The gap between the bottom water seal and the threshold is increased when the miter gate is fully closed.The sealing bolts of the bottom pivot segment are changed from counterbore bolts to through-hole bolts.The strength of all sealing fixing bolts is increased.Two anti-loosening nuts are installed to improve the sealing device's working conditions and reliability.The gap value between the bottom water seal and the threshold is obtain by calculating when the miter gate is fully closed.It is ensured that the bottom water seal is just in contact with the threshold when the miter gate is closed.The results show that the water seal devices of miter gates for the three Gezhouba ship locks are reconstructed，which have good operation effect.