Granular systems are intrinsically far from equilibrium for their many-body and dissipative nature.Driven by external foroes,they can behave like that of solids,liquids,or gases.In dilute granular gases,clusters usually form due to dissipation,which leads to inhomogeneous density distributions.Such a local condensation shows spontaneous symmetry-breaking instability and negative compressibility,just sa droplets form in vapor.In this paper,a three-dimensional model for granular gases under zero gravity is investigated,and calculations predict such a gas-liquid like phace transition.Molecular dynamics simulations show good agreements with the theoretical results.The numerical results shall provide detailed experimental parameters for the further related space exteriments.