"Trade is the important engine of economic development," Mr Xi said at a summit of world leaders in Beijing.
The plan, which aims to expand trade links between Asia, Africa, Europe and beyond, was first unveiled in 2013.
Part of the massive funding boost, which is aimed at strengthening China's links with its trading partners, includes 60bn yuan ($9bn; £7bn) in aid to developing countries and international institutions that form part of the Belt and Road project.
Mr Xi used his speech to assure Western diplomats that the plan, described as the new Silk Road, was not simply an attempt to promote Chinese influence globally.
"In advancing the Belt and Road, we will not re-tread the old path of games between foes. Instead we will create a new model of co-operation and mutual benefit," Mr Xi said at the opening of the two-day summit.
"We should build an open platform of co-operation and uphold and grow an open world economy," he added.
A Chinese idea but for everyone's benefit. That's how Mr Xi presented his Belt and Road vision to drive trade and prosperity through Chinese built infrastructure.
President Putin of Russia and President Erdogan of Turkey were among those applauding from the front row as the Chinese leader talked of a big family of harmonious co-existence and pledged billions of dollars in loans and investment.
But neighbours Japan and India have stayed away from the summit, suspicious that China's development agenda masks a bid for strategic assets and geopolitical ambitions. And some economists are cautious about the viability of projects in areas of political instability and poor governance.
In his keynote address on Sunday, Mr Xi ignored the doubters. He talked of a new model of win-win co-operation, an implicit bid for Chinese global leadership at a time when other big economic powers like the United States and the European Union are preoccupied with internal problems.
Mr Xi said that it was time for the world to promote open development and encourage the building of systems of "fair, reasonable and transparent global trade and investment rules".
"China is willing to share its development experience with all countries. We will not interfere in other countries' internal affairs," he said.
"No matter if they are from Asia and Europe, or Africa or the Americas, they are all co-operative partners in building the Belt and Road."
Mr Xi did not give a timeframe for the distribution of funds pledged for the projects outlined on Sunday.
Leaders from 29 countries are attending the Belt and Road forum, which ends on Monday, including Russian President Vladimir Putin and Turkish President Recep Tayep Erdogan.
Several other European leaders, including the prime ministers of Spain, Italy, Greece and Hungary, are also attending the summit.