The Shanghai Cooperation Organisation (SCO) has set a model for a new type of international relations, Xi said in opening remarks addressing more than 20 world leaders at a two-day summit held in northern China's port city Tianjin.
"We should advocate for equal and orderly multipolarisation of the world, inclusive economic globalisation and promote the construction of a more just and equitable global governance system," he said.
"We must take advantage of the mega-scale market ... to improve the level of trade and investment facilitation," said Xi, urging the bloc to boost co-operation in fields including energy, infrastructure, science and technology, and artificial intelligence.
Putin said the grouping has revived "genuine multilateralism" with national currencies increasingly used in mutual settlements.
"This, in turn, lays the political and socio-economic groundwork for the formation of a new system of stability and security in Eurasia," he said on Monday.
"This security system, unlike Euro-centric and Euro-Atlantic models, would genuinely consider the interests of a broad range of countries, be truly balanced, and would not allow one country to ensure its own security at the expense of others."
Indian Prime Minister Narendra Modi and other leaders from Central Asia, the Middle East, South Asia and Southeast Asia attended the opening ceremony in a major show of Global South solidarity.
The security-focused bloc, which began as a group of six Eurasian nations, has expanded to 10 permanent members and 16 dialogue and observer countries in recent years.
Xi called on organisation partners to "oppose Cold War mentality and bloc confrontation" and to support multilateral trade systems.
That was an apparent dig at US President Donald Trump's tariff war which has disproportionately affected developing economies such as India, whose exports were hit with a 50 per cent levy last week.
China will provide 2 billion yuan ($A428 million) of free aid to member states in 2025 and a further 10 billion yuan ($A2.1 billion) of loans to an SCO banking consortium, he added.
Speaking on the sidelines of the meeting on Sunday, United Nations Secretary-General Antonio Guterres said China played a "fundamental" role in upholding global multilateralism.
Beijing has also used the summit as an opportunity to mend ties with New Delhi.
Modi, who is in China on his first visit in seven years, and Xi both agreed on Sunday their countries are development partners, not rivals, and discussed ways to improve trade ties amid the global tariff uncertainty.
