The World Bank approved a $300 million loan for China yesterday, the bank's largest loan to China since tanks suppressed the pro-democracy movement there last June.

Approval came despite protests in Congress and from Chinese student groups in this country.

The United States contributes more than any other country to the bank, which is the biggest source of aid to the Third World. Patrick Coady, the U.S. executive director, is one of the 22 members on the board that met in private yesterday and approved the loan.

Until last year, China and India were the bank's two biggest borrowers. China borrowed $1.35 billion in the 12 months that ended last June 30. Since then it has borrowed $140 million.

The new loan will go largely for planting trees in 15 Chinese provinces. China can take 40 years to repay it at less than 1 percent interest a year.

Within a week after the Tiananmen Square massacre, bank President Barber B. Conable delayed loans to China worth $780 million, though he continued disbursing loans granted previously. President Bush then asked that new loans be withheld but later said they should be granted only for basic human needs.

Robert Levine, a Treasury Department spokesman, said that the forestry loan qualified under that definition because it provides jobs, fuel and housing material for low-income farmers. It is part of a $500 million project, for which China will provide the other $200 million.

Bank spokesman Peter Riddleberger said another loan of $150 million for roads and waterways in China was indefinitely postponed at yesterday's meeting. He added that the postponement was asked by one of the 22 executive directors, whom he declined to identify except to say that it was not the U.S. representative.