Abstract：This paper, comparing two cases of Lenovo Merging IBM’s PC business and Motorola Mobile, focuses on the factors of the complementary assets’ utility under the behavior of cross-border M&A using the method of cases studies. Acquiring the external complementary assets is one of the most important strategic targets when an enterprise starts the activity of cross-border M&A. However, previous studies drew a conclusion that after finishing the merger, the enterprise which obtained the external complementary assets often got into the destiny of “winner curse”. The enterprise doesn't develop as expected. The complementary assets don't works well in accelerating growth of the enterprise. Based on the comparison of two mergers of Lenovo Group, it is found that several factors influence the utility of the external complementary assets in different stages of the mergers, which are the strategy of the merger, the quality of the complementary assets in the merger activity, and the integration capability after the merger.