The way that pipelines penetrate through the membrane and submerged sealing are two important aspects to the sealing effect of the membrane in the vacuum preloading practice.Two effective methods for pipelines’penetrating through the membrane,i.e.trouser legs forming and flange forming,are expounded respectively.Whether water above the membrane has the sealing effect or not is disputed,non-viscous compressible fluid dynamic model in aerodynamics and the sharp-edged big orifice model in hydraulics are used to approximate the conditions of air leakage only and water leakage only because of the small holes on the membrane.Calculations show that the former condition has a larger magnitude displacement of pore volume than the latter in unit time.Water above the membrane can slow down the loss of the vacuum degree,but still waste energy.Reference can be provided for vacuum preloading projects to penetrate the membrane and overlie water above the membrane reasonably.