The head of mining giant Rio Tinto says he isn't worried about China's slowing growth — and he sees "lots of opportunities" in the world's second largest economy.

"There is no doubt that the Chinese economy is still slowing down, but it is as expected. Even growing 6, and 6 and a half percent, is a massive number," CEO Jean-Sébastien Jacques told CNBC's Eunice Yoon at the China Development Forum in Beijing on Saturday.

Compared with growth rate of Europe, the U.S. and Canada, China's projected expansion of 6 to 6.5 percent is still a "big number," Jacques said.

China is a large-scale buyer of mined commodities from Australia, where Rio Tinto — one of the world's largest metals and mining companies — has major operations.

The U.S. Federal Reserve downgraded its economic outlook for 2019 last week, and now sees growth of just 2.1 percent for the United States this year, down from the 2.3 percent estimate in December.

This month, Europe's central bank cut its growth projection for the bloc — to 1.1 percent in 2019 and 1.6 percent in 2020 — and announced a slew of stimulus measures.

Jacques said that Rio Tinto is well placed to benefit from China's infrastructure spending.

It is "very good for us," he said. "The more iron ore you need, high quality iron ore, the more bauxite, the more copper, the better it is for Rio Tinto ... We are one of the first players here, we've been there for more than a hundred years."