The invention discloses a method, network node and system for realizing clustering based on a random mode and relates to the field of network control. Network nodes divide time after appointed time into continuous time intervals; the time in each time interval is divided into N time periods with preset lengths; the N is a node identity space value; a random number R is allocated to each time period in each time interval; a candidate node identity set is generated according to received node tables broadcasted by adjacent nodes; each node identity in the candidate node identity set is converted according to the random number corresponding to the time period in which the current time is located, thereby obtaining corresponding conversion identities; and the node corresponding to the minimum conversion identity is taken as the cluster leader node. According to the method, the system and the network node, the node identities of candidate cluster leaders are randomized, probabilities that all nodes become the group leaders are approximate, and the problem that energy is liable to exhaust due to the fact that some nodes are taken as the cluster leaders for a long time is effectively avoided.