Aiming at the problem of the large mass of the powder, the long ignition/flame spreading distance along axis and many complex ignition/flame spreading conditions in the large caliber balance guns with long-chamber charges, a two-phase flow model was developed for the designed multi-point ignition/flame spreading construction. By controlling the number of the igniters, the flow process and rules of gas releasing in the igniter tube with different numbers of igniter were obtained. A comparison of characteristic quantity of ignition characteristics including ignition/flame spreading time, ignition/flame spreading pressure and void ratio etc obtained by the single-point ignition, the two-point ignition and the multi-point ignition in the same specification igniters under the same amount of charge was performed. Combined with the test results of multi-point ignition in large caliber balance gun, the calculated results of the multi-point technology were verified. Results show a lot of gunpowder still do not burnt and appear an obvious accumulation phenomenon at about 3.3 ms when the single-point ignition or two-point ignition is used, but almost all the propellants are burned out at about 2.43 ms when the multi-point ignition is used and the distribution of the characteristic quantity is relatively uniform. Therefore, use of the multi-point ignition technology in the large caliber balance guns with long-chamber charges and the other big charges with heavy propellant can effectively improve the ignition/flame spreading time, increase the ignition/ flame spreading stability and restrain the gunpowder accumulation.