Long, who signed a four-year extension with the franchise Sept. 7, 2016, had an $8.5 million cap hit for the 2019 season before taking the pay cut. The terms of the contract weren't disclosed by the team.
The offensive guard missed half of last season with a foot injury he sustained Oct. 28. He played in eight regular-season games last year, and Chicago's wild-card loss to the Philadelphia Eagles.
Long enters his seventh season with the Bears. Chicago originally selected him in the first round (No. 20 overall) of the 2013 NFL Draft.
Long has started 72 of his 73 career games in the NFL, all with the Bears.