[Purpose/significance] This study aims to clarify the triggering mechanism of bystander users' willingness to intervene with Internet illegal and malicious information, so as to provide beneficial reference for the concrete imple⁃mentation path of online information content ecological governance. [Method/process] This study employs the experi⁃mental vignette methodology, introducing the classic bystander intervention model into the context of online illegal and harmful information. It constructs a formation path of bystanders' intervention intention, and further incorporates the protection motivation theory and information content ecological literacy to explore the boundary conditions of this path.[Result/conclusion] The "affective attention → social hazard perception → sense of online responsibility → self-effi⁃cacy" path of bystander intervention intention is applicable in three kinds online illegal and harmful information scenar⁃ios. At the same time, threat appraisal plays a paradoxical "risk incentive" role in bystander intervention contexts, gen⁃erally strengthening the influence of self-efficacy on intervention intention. Outcome expectancy significantly and nega⁃tively moderates the relationship between self-efficacy and intervention intention in the contexts of cyberbullying infor⁃mation and malicious ideological information. Moreover, information content ecological literacy significantly and nega⁃tively moderates the relationship between self-efficacy and intervention intention only in the context of malicious ideo⁃logical information.