The PBOC put 60 billion yuan (nearly $9 billion) into seven-day reverse repos, a process by which central banks purchase securities from banks with an agreement to sell them back in the future.
The reverse repo was priced to yield 2.25 percent, according to a PBOC statement.
Given that 30 billion yuan's worth of repos matured on Tuesday, the central bank effectively injected 30 billion yuan into China's monetary market.
The central bank has adopted repos and other liquidity operations to ease money shortages in the market more frequently this year, rather than cuts in interest rates or the reserve requirement ratio.