[Purpose/significance] This paper aims to clarify the triggering mechanism of bystander users' willingness to intervene with Internet illegal and undesirable information, so as to provide useful reference for the concrete imple⁃mentation path of users' participation in the ecological governance of network information content. [Method/process]This paper uses the grounded theory to identify the factors that trigger bystander users' intention to intervene with ille⁃gal and undesirable information on the network and constructs a trigger mechanism model. Then, ISM-MICMAC is ad⁃opted to clarify the correlation path and hierarchical relationship of trigger factors. [Result/conclusion] The results show that there are the following three trigger pathways:“stakeholder/ cultural literacy/ information literacy→risk per⁃ception→social responsibility→self-efficiency→intervention intention”“involvement level/ social psychological dis⁃tance→social responsibility/ social hazard perception→self-efficiency→intervention intention”and“involvement lev⁃el/ social psychological distance/ bad information content→trigger emotion→intervention intention”. Meanwhile, suffi⁃cient time, report navigation, policy support, social support and platform support directly trigger bystander users’inter⁃vention intention.