Grid information service is an important part of grid systems, which influences performance of grid systems directly. Therefore, it is necessary and urgent to analyze characteristics of grid information service. We analyze performance metrics of grid information service; discuss modeling of grid information and grid information service. As an example, JFreeSim is introduced and focused on simulation of grid information service. JFreeSim realizes many entity modeling and communication mechanisms among all entities, and makes system simulation in accord with the characteristic of the grid environment. Examples indicate that JFreeSim can provide users with flexibility in configuring and satisfying requirements of different information service modeling.