BEIJING—China’s central bank is planning to inject 200 billion yuan ($32.6 billion) into the banking system, according to financial executives briefed on the matter, as recent credit-easing measures have failed to push the world’s second-largest economy back to stronger growth rates amid deepening worries about a global slowdown.

The latest effort by the People’s Bank of China, which will offer funds to about 20 large national and regional banks, follows last month’s move to pump 500 billion yuan into the country’s five major...