The British star has signed a deal with London publisher John Blake for the worldwide release of her book, which will be created with the help of a ghost-writer.
Frost, who divorced Law in 2003, will reportedly reveal "all the gossip" from her colourful life, including her relationship with the Hollywood hunk, as well as her first husband, Spandau Ballet star Gary Kemp.
The fashion designer is also expected to divulge secrets from her longtime friendship with supermodel Kate Moss.
Publisher Blake tells The Bookseller.com, "You couldn't wish for more in an autobiography. We aren't sure of the finer details but we expect it to contain pretty much everything. The thing about Sadie is she has a very good sense of humour and is very self-deprecating, so she is prepared to send herself up. We were thrilled to be offered it."