Abstract: Owing to the inelastic collisions and frictions among particles, granular systems are dissipative in nature. This intrinsic dissipative nature causes clustering in granular gas systems,the condition when this phenomenon happens will be helpful for gaining knowledge of pattern formations in non-equilibrium complex systems. The clustering phenomenon in granular gas can be modeled theoretically using phase-separation of van der Waals-like molecules. The prediction has been verified by molecular dynamics numerical simulations. However, due to the influence of the gravity, experimental verification is difficult in laboratory. SJ-10 provides us such an opportunity to gather important experimental evidences.