Since last decades, there has been a growing interest in the human/social dimensions of natural resources governance especially the structure of social networks in achieving to successful co-management of natural resources. Network analysis as a suitable tool in optimum planning of the “network management” of rangeland in regional scale, can improve inter-organizational decision-making and coordination among key actors. Trust development and mutual relations among various actors is a key factor in policy of rangeland co-management issue. In this study, trust and collaboration networks between informal and formal institutions and rangeland users in co-management process have been investigated. Social network analysis as a quantitative method has been implicated in this research. The results of this study indicate that “Veterinary Office of Taleghan” and “Village Council” can play a key role in policy and planning of rangeland co-management which is related to higher density of trust and collaboration ties. Moreover, trust and collaboration networks among the Veterinary Office and rangeland users have more sustainability than these in related to other institutions. However, the sustainability of networks among all of institutions and rangeland users has low level. Statistical results show there is a high correlation (70%) between trust and collaboration networks and also 50% of collaboration changes are related to trust factor. Also, it can be state that lack of trust and collaboration between the Natural Resources Office and rangeland users is a key challenge for initiating of rangeland co-management. Finally, social network analysis helps manager and planner in detecting of the challenges of rangeland co-management and policy in tune with solving these challenges.