The paper mainly discusses the functional model and the state of RRC sublayer in LTE system，as well as the connection eatablishment process of RRC sublayer when it communicates with another user normally．Traditionally there are two large states which are idle and connection．Now，it divide them into three sub-state separately．In addition，it defines the RRC to the high-level and to the underlying primitives，by the above method，it can systematically describes the connection eatablishment process of normal communication of LTE system，combined flow chart to illustrate this process．