The paper investigates how the maturity structure of local government debt influences corporate financial stability. Using a matched panel data set of Chinese A‐share listed firms between 2009 and 2023, we document that a shift toward longer public debt maturity substantially raises corporate stock price crash risk. This effect operates through three channels that induce corporate maturity mismatch, lower investment efficiency, and increase default risk. We further show that structural monetary policy can mitigate the adverse consequences, while debt issuance intensity exhibits a nonlinear threshold. These findings identify a significant microtransmission mechanism through which local government debt maturity decisions amplify financial fragility.