Propellant is one of the most important material of the missiles systems. In general, the propellant has an usable period in order to assure performance and expired propellant should be discarded safely. However, this incineration process is extremely dangerous because the propellant is consisted by highly reactive materials such as nitrocellulose (NC) and nitroglycerine (NG). In these days, fluidized bed is considered as an advanced reactor for the incinerating process because of the particulate propellant is incinerated consistently and efficiently. Fluidizing and mixing characteristics are quite significant in design an effective and safe fluidized bed propellant incinerator. In this study, the computational fluid dynamics (CFD) model is established to evaluate fluidizing and bubbling behaviour in the fluidized bed propellant incineration. Eulerian-Lagrangian coupled method is used to rigorously simulate fluidization behaviour of the propellant particles in the bed. Various process conditions such as mass flow of feed and air injection rate are considered for the model to analyse fluidization effect. The fluidized bed is designed cylinder shape and its diameter is 2m and height is 9m for the target NG/NC disposal rate 20,000 t/y and diameter of propellant is assumed 3.0mm. TNT is incinerated for applying other propellants by using TNT equivalent method. In addition, incineration reaction of propellant is contemplated. Therefore the 40% of fluidized bed is filled with sand to prevent damage according to overpressure and high temperature by incineration of propellant. The simulations are performed with changing air injection velocity to find optimal conditions of fluidization. Fluidization begins to be observed at 1.0 m/s of air injection rate and meaningful fluidization is observed at 1.5 m/s of air injection rate. When air injection rate is 2.0 m/s, fluidization is better than others and maximum temperature is acceptable. As a result, 2.0 m/s of air injection rate is optimal condition. This research will be of help to demilitarize old propellant safely and economically and can be useful data to build incineration facilities.