The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for forwarding system information for a remote UE by a relay UE in wireless communication system, the method comprising: establishing a link between a remote UE and the relay UE for communicating between the remote UE and the network via the relay UE; receiving assistance information including a serving cell identity of the remote UE from the remote UE; checking whether a serving cell identity of the relay UE and the serving cell identity of the remote UE are same or not; and forwarding system information block (SIB), which was already received by the relay UE from the network, to the remote UE via the link if the serving cell identity of the relay UE and the serving cell identity of the remote UE are different. The UE is capable of communicating with at least one of another UE, a UE related to an autonomous driving vehicle, a base station or a network.