In response to adverse shocks, managers of money market funds (MMFs) typically resort to fire sales to prevent concentrated redemptions. However, such behavior may trigger risk contagion among MMFs, potentially leading to a systemic crisis. This paper proposes a fire sales risk contagion model based on the “fund-asset” bipartite network and measures the total spillover loss, systemic vulnerability and systemic importance of MMFs under a unified framework. Meanwhile, this paper examines the effects of fund characteristics, fund liquidation strategies, and risky asset prices on systemic risk. Using bond market transaction data and Chinese MMFs’ financial data, our findings reveal that the interconnectedness between MMFs and the bond market serves as a core driver of systemic risk generation. Ignoring spillover effects caused by fire sales significantly underestimates the systemic risk. Higher similarity in asset portfolios leads to increased vulnerability and systemicness of the MMFs. Fund size significantly contributes to the systemicness of the MMF. The price levels of risky assets arising from different liquidation rules account for the disparities in systemic risk exposure among MMFs. These results provide crucial insights for financial regulatory authorities to implement appropriate interventions against risk contagion among MMFs, and enhance the evaluation and supervision framework for important MMFs.