In line with President-elect Donald Trump's proposals, Steve Mnuchin told CNBC on Wednesday his focus as Treasury secretary will be stimulating economic growth and creating jobs through tax reform.

"By cutting corporate taxes, we're going to create huge economic growth and we'll have huge personal income," Mnuchin told "Squawk Box," confirming he has been tapped for Treasury secretary.

Reducing the corporate tax rate from 35 percent to 15 percent will be a major goal for the Trump administration, the former Wall Street executive said.

Mnuchin said he was confident the new administration would be able to expand gross domestic product growth from the current 3.2 percent.

"Our most important priority is sustained economic growth, and I think we can absolutely get to sustained 3 to 4 percent GDP, and that is absolutely critical for the country," Mnuchin said. "To get there, our number one priority is tax reform. This will be the largest tax change since [President Ronald] Reagan."

In addition, he said he wants to simplify taxes for the average citizen. "Taxes are way too complicated, and people spend way too much time worrying about ways to get them lower," he said.

Mnuchin was Trump's campaign finance chairman during the election. Previously, he was chairman of Dune Capital Management and worked at Goldman Sachs and the Soros Fund Management. He also co-founded OneWest Bank Group.

Dune Capital funded Hollywood films including "Avatar."

Correction: The corporate tax rate is 35 percent. An earlier version misstated the figure.