Faced with the challenges of a complex and severe external environment and the critical deepening stage of domestic structural adjustment, a proactive fiscal policy that is moderately intensified, of higher quality, and more efficient is not only crucial for stabilizing expectations but also serves as a significant safeguard for promoting both qualitative improvement and quantitative rational growth of the economy.Production networks are incorporated into a general equilibrium model to theoretically analyze the transmission mechanism of fiscal policy shocks on sectoral output fluctuations.The theoretical analysis reveals that within the production network, the transmission of government spending shocks to sectoral output follows a bottom-up direction.An empirical analysis is then conducted using input-output tables from the World Input-Output Database (WIOD), verifying the significance of the upstream network effect of fiscal policy.Heterogeneity analysis shows that the upstream network effect is significantly negative in sectors with low sensitivity and low upstreamness, influenced by factors such as the price elasticity of supply and demand and the distance to final demand. This stands in sharp contrast to the positive effect observed in sectors with high sensitivity and high upstreamness. In addition, sectoral structure factors significantly moderate the effects of government spending shock.It is argued that while leveraging the demand expansion function of government spending, policymakers should fully prioritize sectoral spillover effects.By amplifying the fiscal multiplier through production networks, fiscal policy can achieve higher quality and efficiency.