In the complex communication environment formed by social media technology empowerment and group interaction, college students’ online expression behaviors present irrational dynamic evolution characteristics. The aim is to reveal the mechanism of irrational online expression of college students and provide governance suggestions for network ecological governance and youth value guidance. Integrating WSR system methodology and Grounded Theory, we extracted the core elements through in-depth interviews and three-level coding analysis, and constructed an explanatory model of “technology empowerment-cognitive simplification-behavioral feedback-feedback regulation”. Technological empowerment drives irrational behaviors through three paths: the anonymity mechanism dissolves moral constraints, algorithmic recommendation exacerbates the information cocoon, and instantaneous communication compresses the space for rational thinking; the behavioral dimension forms the mechanism of “anti-taming of data”, and the data output from irrational expression continues to reconfigure the technological environment, forming a closed loop of the dynamic game. The innovation is reflected in the integration of methodology and dynamic evolutionary explanation model, which provides a new path for the governance of irrational network expression.