A scientific mechanism for the allocation and use of government science and technology funds can effectively stimulate corporate innovation vitality, which is significant for cultivating new quality productive forces. A-share non-financial listed companies from 2010 to 2023 were used as the sample. Government innovation subsidies were divided into pre-event subsidies and post-event incentives. Based on the enterprise life cycle perspective, the heterogeneous effects of subsidy timing on the quantity and quality of enterprise innovation were empirically tested. It is found that pre-event subsidies have a significant positive impact on innovation in enterprises in the growth, maturity, and decline stages, with the strongest effect observed in the maturity stage. Post-event incentives incentives significantly increase the quantity of innovation only in declining enterprises but lead to a decline in innovation quality. Mechanism tests show that increasing R&D investment is an important channel through which both pre-event subsidies and post-event incentives promote corporate innovation. Additionally, post-event incentives can indirectly promote innovation by curbing corporate financialization and attracting R&D human capital. Further analysis reveals that pre-event subsidies are more effective in motivating mature and declining enterprises to increase R&D intensity per unit, while post-event incentives tend to induce strategic innovation in growing and mature enterprises. State-owned enterprises show a significant positive response to high-quality innovation only when receiving post-event incentives. Based on the empirical findings, a subsidy system characterized by precise timing, life cycle adaptation, and ownership classification is proposed. It provides practical insights for improving the efficiency of fiscal fund utilization.