Faced with "the Belt and Road" initiative which was proposed by China, the cognition and acceptance of EU countries have been different. Some EU countries emphasize the geopolitical threat of the "Belt and Road "initiative to Europe, while some EU countries pay more attention to potential economic development opportunities. Up to now, 18 EU countries have joined "the Belt and Road " initiative, but there are still 9 EU countries that choose to maintain a wait-and-see attitude towards “the Belt and Road” initiative. What are the reasons for the differences in choices among EU countries on this issue?

   Existing researches are mostly limited to a single subject or a single perspective, focusing on the EU or a certain country's cognition of “the Belt and Road" initiative, but ignoring the interactions between different subjects and the connections between influencing factors. Based on this, on the basis of combing the research results at home and abroad, this article uses the research method of Fuzzy Set Qualitative Comparative Analysis (fsQCA) to study the necessary condition and combination of sufficient conditions that affect EU countries' joining/not joining "the Belt and Road" initiative. This article proposes relevant hypotheses from six aspects: the domestic economic conditions of EU member states, the conflict of interest with China in overseas markets, the right to speak in the EU, populism, recognition of European collective identity, and institutional differences with China. This research selects authoritative variables for testing. Research shows that the combination of factors such as "low recognition of European collective identity" and "small distance from China's political system" is the most significant way to promote EU countries to join "the Belt and Road" initiative. System differences are an important factor that affects whether EU countries join "the Belt and Road " initiative. Domestic economic conditions have produced differences in the impact of EU countries’ decision-making: EU countries with poor domestic economic performance tend to join "the Belt and Road " initiative, but EU countries with moderate domestic economic performance may not necessarily refuse to join "the Belt and Road " initiative. In addition, populism has no definite influence on the issue of differences in EU countries’ choices of "the Belt and Road" initiative.