The present disclosure relates to method and system for user equipment (UE)-initiated network slice registration and traffic forwarding in telecommunication networks. In an embodiment, for network slice registration, UE transmits a registration request to an AMF via a base station of telecommunication network. In response to the registration request, the AMF transmits a registration accept response comprising network slice selection assistance information (NSSAI) to the UE. For traffic forwarding, the UE transmits a PDU session establishment request comprising single NSSAI to the telecommunication network. The base station of the telecommunication network maps the single NSSAI to a Flow Label field of IPv6 header and transmits to DPAF via specific SLF of the telecommunication network. DPAF compares QoS transport characteristics of the single NSSAI with QoS transport characteristics of the NSSAI in the DPAF of the telecommunication network and transmits a PDU session establishment response to the UE based on comparison.