Tate Britain, on London's south bank, is the national gallery of British art with exhibits from the Renaissance to the present day.
It will showcase previously unseen documents from leading artists of the past century including Barbara Hepworth, Stanley Spencer and members of the Bloomsbury group.
A £2.2m donation towards the project was made by businessman Hyman Kreitman and his wife Irene, with the centre due to open in spring 2002.
Tate Britain, on London's south bank, is the national gallery of British art with exhibits from the Renaissance to the present day.
The collection of artists' manuscripts, correspondence, diaries, sketchbooks, photographs and press cuttings has been available to the public before, but space has been limited.
The new library will include two reading rooms with space for 40 visitors, storage room and access to electronic media.
The Kreitman family has made substantial donations to the gallery in the past.
Among the items of most interest will be the many love letters written by or to artists including John Nash and Dora Carrington, Ben Nicholson and all three of his wives, and Stanley Spencer to his wife.
Spencer even continued to write to his wife after she died.
'Grateful'
In 1955, five years after her death, he wrote that their love was "a wonderful desecration of most of the childhood hopes, because it is sexual and non-innocent, but it is grown-up".
Nicholas Serota, the director of the Tate, said: "Research and scholarship lie close to the heart of any museum.
"This scheme will bring together library and archive materials and make them more widely available in new reading rooms.
He added that they were "enormously grateful" to the Kreitman family for providing such a cornerstone in the work of Tate.