A total of 172 countries, regions and international organisations from five continents will showcase their development achievements and international image at the first China International Import Expo (CIIE), reports Xinhua news agency.
More than 3,600 companies from different countries will hold discussions and seek common development with over 400,000 purchasers from China and overseas.
The CIIE is "a major policy for China to push for a new round of high-level opening-up and a major measure for China to take the initiative to open its market to the world", Xi said when delivering a keynote speech at the opening ceremony.
He underscored the role of economic globalization, saying that it is "an irreversible historical trend" and provides strong momentum for world economic development.
"All countries should be committed to opening up and oppose protectionism and unilateralism in a clear-cut stand," Xi said, calling for joint efforts to build an open world economy.
The fair will feature various quality exhibits ranging from German machine tools, Japanese robots and US medical equipment to Australian wine, Brazilian farm produce and South Sudanese handicrafts.
With the slogan "New Era, Shared Future", the expo is the brainchild of Xi and is set to become a platform for win-win economic cooperation and a landmark project in the country's higher-level opening up.
China will stimulate the potential for increased imports, continue to broaden market access, foster a world-class business environment, explore new horizons of opening up, and promote international cooperation at multilateral and bilateral levels, Xi said.
The expo comes at an inflection point as China transitions to high-quality development and shifts from the world's workshop to the world's market, with the world's biggest middle-income population demanding higher-quality consumer products.
Xi announced that China's imported goods and services were estimated to exceed $30 trillion and $10 trillion, respectively, in the next 15 years.
China has been the world's second largest merchandise importer for nine consecutive years.
This year marks the 40th anniversary of China's reform and opening up, and has seen a flurry of concrete measures taken by the country to open its doors wider.
"China will not close its door to the world and will only become more and more open," Xi added.