A variety of functions of nanoparticle thin films are expected to be realized by two- or three-dimensional ordering of a large number of nanoparticles. The coating-drying process that induces a self-ordering of nanoparticles in a liquid phase is one of the most promising methods for industries. However, the structures of ordered nanoparticles are designed by empirical control of some process conditions in industries. We have modeled the dynamics of two-dimensional self-ordering of nanoparticles in a liquid phase, and have simulated the drying processes of nanoparticle suspensions. The relationships between the process conditions and the structures are derived from the simulation results as well as some experimental data. We have proposed three non-dimensional variables to represent principles of the two-dimensional self-ordering of nanoparticles: 1) Long-range inter-particle energy ratio, 2) Particle binding energy ratio, 3) Particle travel time ratio. These variables are functions of some process conditions, and the structures of ordered nanoparticles can be estimated by sets of these variables.