Chicago announced the moves on Monday.
Barth was booted after missing a game-tying kick in Sunday's game against the Detroit Lions. The Lions beat the Bears 27-24 at Solider Field.
The kicker was 1-for-2 in the loss, making a 23-yard attempt before missing wide right on a 46-yard attempt with eight seconds remaining. Barth, 31, is 11-of-16 this season and has made all of his 17 extra point attempts. He has netted 68.8 percent of his attempts, the lowest percentage of his career. Barth spent the first year of his career with the Kansas City Chiefs before joining the Tampa Bay Buccaneers.
He spent five seasons with the Buccaneers and a season with the Denver Broncos before joining the Bears in 2016.
Santos, 25, has made nearly 85 percent of his career attempts. He joined the Chiefs in 2014 before getting released in September. Santos was dealing with a groin injury. He had made all three of his attempts this season and hit a career-best 88.6 percent of his attempts in 2016 for the Chiefs.
The Bears have lost three games in a row, including two straight to NFC North opponents. Chicago (3-7) faces the 9-1 Philadelphia Eagles at 1 p.m. Sunday at Lincoln Financial Field.