The present invention relates to a wireless communication system that counts UEs using an MBMS, and a method thereof. The wireless communication system is connected with a UE through a radio link, and includes a Node B and a controlling radio network controller (CRNC). The Node B receives sequence setting information on a sequence included in a preamble transmitted from the UE from a network manager. The CRNC controls the Node B, detects a sequence according to whether to use an MBMS based on the sequence setting information, and performs a counting process for counting UEs based on whether the UE uses the MBMS. According to the present invention, counting of UEs using an MBMS can be efficiently performed by using a predetermined sequence. Particularly, the counting process can be simplified by reducing complexity in access probability management of a network manager, thereby increasing efficiency in data transmission by reducing signaling for random access probability and omitting a random access probability calculation process.