The CBS, valued at 2.5 billion yuan (363.5 million U.S. dollars), are open to primary dealers for bidding at a fixed rate at 0.25 percent, according to a PBOC statement.
The swap will mature on June 27, 2020. Following the first CBS operation in February 2019, the new operation aims to "raise the liquidity of banks' perpetual bonds and support their issuance of perpetual bonds," the PBOC said.
The CBS scheme allows dealers to swap the perpetual bonds they hold for central bank bills, which will effectively boost market demand for perpetual bonds but have a neutral impact on liquidity in the banking system.
Perpetual bonds are fixed-income securities with no maturity date and are not redeemable but pay a steady stream of interests forever.
The tool is often used to replenish capital for commercial banks.
In January, the Bank of China issued the first-ever perpetual bonds by a Chinese bank, which were oversubscribed by institutional investors.