Abstract: Enhancing total factor productivity (TFP) serves as the driving force behind high-quality economic development. By constructing a Cournot duopoly model of two countries, this paper compares the TFP differences among companies without M&As, domestic M&As and cross-border M&As, and empirically examines the mechanism of how M&A activities influence TFP by using the data of 1, 229 domestic M&As and 111 cross-border M&As involving Chinese listed companies from 2008 to 2020. This paper employs propensity score matching and time-varying difference-in-differences (DID) methods. The results show that:(1) both domestic M&As and crossborder M&As significantly enhance TFP, with cross-border M&As exerting a greater effect. This phenomenon is particularly significant for non-state-owned enterprises, high-tech companies and companies with low financing constraints. When the bilateral political relationship is friendly and the host country's institutional quality is high, the above phenomenon is also particularly significant; (2) further research shows that cross-border M&As play a stronger role in improving TFP through stronger innovation and management synergies. The distinguishing factor lies in the market monopoly effect, which negatively impacts TFP for domestic M&As but lacks significance for cross-border M&As. The combination of these three effects ultimately leads to a significantly weaker TFP improvement for domestic M&As compared to cross-border M&As. In the context of ongoing trade disputes, it is of great significance for the improvement of TFP and highquality economic growth to encourage Chinese companies to "go out" and integrate external resources, and to actively create a market environment of fair competition to facilitate the integration of internal resources.

Key words: domestic M&As, cross-border M&As, total factor productivity, PSM-DID