Under the new rules, banks will be allowed to use up to 60 percent of reserves for credit operations, an increase from the 50-percent limit announced on July 25.
The bank said the move would free up an additional 10 billion reals ($4.5 billion) in credit.
It comes on the heels of the July 25 stimulus measures, which the bank said would free up $13 billion in additional credit. The maneuvers come as the clock ticks down to Brazil's October presidential elections.
Incumbent Dilma Rousseff is seeking a second four-year term, but battling to convince voters she can inject new life into an economy that has averaged 2.1-percent growth during her time in office, down from 7.5 percent in 2010, the year she won election.
Finance Minister Guido Mantega also announced a new credit program to boost the real estate sector.