3 March 2002 was a very significant day to Switzerland and his people. Both the people and the cantons (the double majority required) accepted the popular initiative on Switzerland’s membership to the United Nations. Although it’s “just a toe cross the line”, Switzerland became the 190th member of the United Nations eventually. The essay aims to study how international environment affected the country’s foreign policy and the moving of Switzerland’s traditional neutrality in and after the Cold War. And, analyze the reasons of Switzerland’s joining the UN.