This paper proposes a possible application of quantum key distribution in multi-user network. In modern networks, variety of multiple access technologies are being used for multiuser access purposes. In this paper, we focus on a type of widely used MAC (Media Access Control) protocol—CSMA/CA, and analyse its use for the quantum key distribution in the network. This work is based on a successful experiment that implemented the quantum key distribution over 200 km by using the decoy-state method. The secret key generation rate as the main indicator of the performance is given, including the relationship between it and the number of stations in the network, and the relationship between the key generation rate and the transmission distance under the multiple access condition as well.