This paper proposes that behavior nonlinearity should be the focus of future re-search of particle-fluid systems, which includes the intrinsic aspect resulting from particle-fluid interaction and the secondary aspect related to external factors and non-}deality of material properties. The intrinsic nonlinearity leads to bifurcation, chaos and self-organization, which is complicated further by the secondary nonlinearity. The concept of multiple resolution is proposed for analyzing such a complicated system，that is, the superficial motion into extremum and dynamic aspects，the total energy consumption into reversible and dissipative components,the whole process into ordered and disordered branches，and the global structure into different scales. Computer graphic simulation based on the assumption of two discrete media with different dimensions is also proposed to study nonlinear behaviors in the system.