A fin field effect transistor (FinFET) device structure with dummy fin structures and method for forming the same are provided. The FinFET device structure includes an isolation structure over a substrate and a first fin structure extended above the isolation structure. The FinFET device structure includes a second fin structure embedded in the isolation structure and a liner layer formed on sidewalls of the first fin structures and sidewalls of the second fin structures. The FinFET device structure also includes a material layer formed over the second fin structures, and the material layer and the isolation structure are made of different materials.