The Department for Education and Employment has given Cotham and Fairfield schools permission to change their status and end selection. The schools will have a comprehensive intake from 2000.
It is the third attempt by the schools to become comprehensive. Previous requests were turned down by the Conservative government.
The news was welcomed by Valerie Davey, Labour MP for Bristol West.
James Wetz, head of Cotham, said: "The two grammar schools were seen as an anachronism in the city where the education system is comprehensive. Instead of having pupils from 36 feeder primary schools, we will become a community school serving families in north central Bristol, and I welcome that."