In modern collaborative and distributed applications, authenticated group key agreement (GKA) is one of important issues. Recently identity (ID)-based authenticated GKA has been increasingly researched because of the simplicity of a public key management. In this paper, we present a formal treatment on ID-based authenticated GKA, which extends the standard GKA model. We present two GKA protocols which use a bilinear-based cryptography: one is a bilinear variant of Burmester and Desmedt protocol  and the other is ID-based authenticated protocol based on the former protocol. Our protocols are scalable and 2-round protocols with forward secrecy. In particular, the ID-based authenticated GKA protocol provides a batch verification technique, which verifies the validity of transcripts from other group players simultaneously and improves computational efficiency. We then prove their securities under the decisional bilinear DH and computational DH assumptions.