This paper investigates the varying impact of government subsidies on corporate investment efficiency using micro-level data from Chinese listed firms. Through meticulous compilation of information on government subsidies revealed in financial statements, and the implementation of an innovative categorization methodology based on the nature and timing of funds (ex-ante versus ex-post), we shed light on the divergent effects of these subsidies. Our findings are as follows: (1) Government subsidies enhance corporate investment efficiency, yet their effects exhibit asymmetry by alleviating underinvestment while exacerbating overinvestment. (2) Functional subsidies exert a stronger influence on investment efficiency compared to selective subsidies. Specifically, functional subsidies prove more effective in addressing underinvestment, but also possess a higher likelihood of exacerbating overinvestment. (3) State ownership, firm size and dividend payments lead to heterogeneity in the effects of subsidies. (4) Corporate financial constraints serve as one of the mechanisms through which subsidies affect investment efficiency. This suggests that firms with easier access to financing may not effectively utilize subsidies, while those facing severe financial constraints are less prone to misusing them.