A method for determining Quality of Service (QoS) level is provided. The method includes: assigning, by a Coaxial-cable Line Terminal (CLT), a QoS level for a user terminal; sending, by the CLT, relevant information of the assigned QoS level to a Coaxial-cable Network Unit (CNU); and determining, by the CNU, a QoS level for a packet sent by the user terminal according to the relevant information of the assigned QoS level. A system for determining QoS level is provided. The system includes: a CLT and a CNU. A CLT and a CNU are also provided. The solution enables a coaxial-cable network unit to satisfy the QoS requirements of user terminals, and reduces the producing cost of the coaxial-cable network unit.