The 35-year-old Smith is entering the final year of his contract and was scheduled to make $2.109 million.
Smith is the second longtime Steelers player to be told he will be released in two days, joining receiver Hines Ward, who was told he will be cut by the team after 14 seasons in Pittsburgh.
Smith's season ended in October when he was placed on injured reserve with a neck injury. It was the third straight season that injuries have limited Smith. He played in only 11 games spanning the 2009 and 2010 seasons because of shoulder and triceps injuries and appeared in just four this season.
Smith, a 1999 fourth-round draft pick by the Steelers out of Northern Colorado, was possibly the most unheralded figure on the Steelers defenses. From 2000 to 2008, when Smith had double-digit starts, Pittsburgh ranked in the top 10 in defense all nine years including four as the top-ranked unit. During his career, Smith had at least four sacks in six seasons and is 10th on the team's all-time list with 44.
Information from ESPN.com's John Clayton and The Associated Press was used in this report.