The pledge, made at a forum here on China-Africa cooperation, is double the amount Beijing agreed to lend to Africa at the last forum in 2009.
Hu said the loans would focus on supporting infrastructure, manufacturing and the development of small businesses in Africa, although he did not specify what time period they would cover.
"China and Africa's destinies are closely linked, Chinese and African friendship is deeply rooted in the hearts of the people on both sides," he said, delivering an opening address to an audience of African leaders.
"China sincerely supports African countries as they pursue their own development paths, and will sincerely assist African countries in strengthening their ability to develop independently."
Hu also promised training and scholarships for African professionals and students, assistance with healthcare and customs and financial support for the African Union.
Beijing's involvement in Africa dates back 60 years, when Chinese workers arrived to lay railway tracks and roads.
But there has been a surge in investment in the past 15 years as Beijing has sought to tap into Africa's natural resources, and China became the continent's largest trading partner in 2009.
Trade between the Asian powerhouse and the continent hit a record $166.3 billion last year, from less than $20 billion a decade earlier and up 83 per cent on 2009, according to government data.
Africa's rich natural resources are its main export to China, which needs minerals to fuel its massive economic growth, while the continent's major imports are mechanical or electrical products.
UN chief Ban Ki-moon, speaking at the forum, said cooperation with China was creating opportunities for African countries to diversify their economies, create jobs and improve healthcare and education.
South African President Jacob Zuma thanked China for treating African countries as equals, but he cautioned against allowing an unequal trade relationship to persist in which Africa mainly supplied raw materials.
"This trade pattern is unsustainable in the long term," he told the China-Africa Cooperation Forum.
"Africa's past economic experience with Europe dictates a need to be cautious when entering into partnerships with other economies.
"We are particularly pleased that, in our relationship with China, we are equals and that agreements entered into are for mutual gain."
Once seen as strictly interested in extracting raw resources and investing in infrastructure, China has interests on the continent that are increasingly shifting to investing in institutions and governments, experts say.
Its aggressive move into the continent has at times caused friction with locals, however, with some complaining that Chinese companies import their own workers, flout labour laws and mistreat local employees.
Zambia's current president tapped into anti-Chinese sentiment to win office in 2011, one year after two Chinese managers shot at 11 local workers protesting over poor pay and work conditions.
In Namibia earlier this year, Chinese Foreign Minister Yang Jiechi acknowledged that problems existed.
"I am not saying every Chinese company here behaves in a perfect way. If not, I hope Namibia tells us and we do our best to solve it," he said. "We told our companies to adhere to laws here."