The deal -- which military experts say could be worth more than USD 2 billion (1.87 billion euros) -- represents the first time a foreign state has purchased the Su-35.
A representative of Rostec, speaking to AFP, confirmed a deal had been reached but declined to give details on the price and timeframe for delivery.
Moscow and Beijing have reportedly been in talks about the sale for three years, with Chinese media reporting in 2013 that the country had agreed to their purchase.
"It was the expected amount," he told AFP.
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Moscow and Beijing, which were rivals during the Cold War, have strengthened cooperation in recent years to counterbalance perceived dominance by the United States
The sale will also help fill Russia's state coffers as its economy has been reeling from low oil prices and Western sanctions imposed over the Ukraine crisis.
Rostec head Sergei Chemezov told Russian media earlier this month that Moscow was in talks with the United Arab Emirates for the sale of Su-35s.