The similar particle assembly (SPA) model proposed for large-scale discrete element method simulation was validated. The SPA model describes the scaling law for the motion of particles in an assembly, which is derived from the equation of motion of a particle. In the SPA model, particles with similar physical or chemical properties are represented by a single particle, which is called the representative particle. The local assembly of particles in the original bed is supposed to be maintained in the bed with the representative particles. The SPA model was validated by numerical simulations of a 2D fluidized bed of noncohesive and cohesive particles. Using the SPA model, the flow behavior of the representative particles of a certain magnification can be made similar to that of the original particles with significantly less computational load. A good approximation of bubble size distribution between the SPA bed and the original bed was obtained. (C) 2011 American Institute of Chemical Engineers AIChE J, 58: 87-98, 2012