It follows an inconsistent year for Sri Lanka who suffered their first ever Test loss to Bangladesh and a whitewash in South Africa.
The South African, who first coached the side from 2012 to 2014, had signed a contract until the 2019 World Cup.
The decision comes before Sri Lanka 's one-day series against Zimbabwe, starting on Friday.
The announcement comes after the board launched an investigation on Thursday into comments by fast bowler Lasith Malinga.
He compared the country's sports minister to a "monkey".
Ford previously worked with county club Surrey and was the director of cricket at Kent.
"It's been a privilege to work with these talented young men over the past 15 months ," he said "Their passion for the sport is inspiring, as is indeed this nation's."
"I wish Sri Lanka Cricket and the boys the very best, and I must offer a word of advice to the young men - always believe in yourself, believe in your team, and play from your heart."