Abstract: This paper improves the mathematical model for the high pressure air blowing in ballast tanks proposed by other researcher by incorporating the effects of gravity， and the difference between the original model and the improved one is presented. To verify the credibility of the improved model， an experiment of high pressure air blowing was carried out， which shows that the improved model can be well applied into the design and optimization of the blowing system. Finally， the impact of certain factors on the blowing procedure is discussed. It is observed that the mass flow rate does not increase along with raise in the outlet area when the latter reaches a certain threshold， and the blowing rate may not change much when the diameter of the nozzle throat increases to a certain value.