"It's the first time that the pricing of such a big listing - the largest in human history - has been determined outside New York City" he told the Bund Summit in the eastern financial hub of Shanghai.
"We didn't dare to think about it five years ago, or even three years ago. But a miracle just occurred," he told the audience, which included officials from China's regulators.
He did not give exact details of the pricing which is expected to be officially announced next week.
Backed by Chinese e-commerce giant Alibaba, Ant plans to list simultaneously in Hong Kong and on Shanghai's STAR Market in the coming weeks.
Sources have said the listing could be worth $35 billion, surpassing the record set by Saudi Aramco's $29.4 billion float last December.
Ma said the financial and regulatory system stifles innovation, calling for a revamp to extend financial services to more small firms and individuals on the basis of technology - an ethos that Ant is largely based on.
He said the global system established after World War II is outdated and too risk-averse, calling the Basel Committee on Banking Supervision "an old men's club" and warning that risks are accumulating in the whole economy.
In China, banks still operate with a strong "pawnshop" mentality, demanding collateral and guarantees before lending, a model that will fail to fuel future growth, he said.
Instead, he said a new, inclusive and universal banking system that lends to small businesses and individuals on the basis of big data should be established.
Ant, which has an extensive payment and micro-lending business that is largely based on big data, has faced rising scrutiny from regulators.
"Today's financial system is the legacy of the Industrial Age," Ma said. "We must set up a new one for the next generation and young people. We must reform the current system."
(Reporting by Samuel Shen and Brenda Goh; Editing by William Mallard)