Against the backdrop of global intelligent transformation in manufacturing, this study examines the impact mechanism of artificial intelligence (AI) on firm-level total factor productivity (TFP) using data from manufacturing companies listed on the Shanghai and Shenzhen A-share markets from 2016 to 2023. It employs a two-way fixed effects model and a mediation effects model. Findings reveal: (1) AI significantly enhances firm-level TFP through dual pathways: strengthening technological innovation and reducing operational costs;(2) Heterogeneity analysis reveals stronger AI effects in technology-intensive firms and eastern regions. Based on these findings, manufacturing enterprises are advised to deepen "AI+R&D" integration, promote technological convergence, and maximize AI's productivity-enhancing potential to accelerate intelligent transformation.