First phase: The twelve clubs played each other in a double round-robin system. The eight best teams qualified to the Final phase, with the best teams and the best hinterland teams in each round earning one bonus point. the bottom two teams in the sum of both rounds were relegated.
Final phase: The eight remaining teams played each other in a double round-robin system; the team with the most points won the title.
Updated to match(es) played on August 23, 1981. Source: RSSSF.com Rules for classification: 1) points; 2) wins; 3) goal difference; 4) number of goals scored.
Updated to match(es) played on October 7, 1981. Source: RSSSF.com Rules for classification: 1) points; 2) wins; 3) goal difference; 4) number of goals scored. Notes:
^ abIn case of ties between either the overall best teams or the best hinterland teams, a nextra match would be played. After Novo Hamburgo beat Inter de Santa Maria in the last round, equaling them in points, it was decided that instead of holding the playoff in another date, extra time and penalties to define the 'hinterland champions' would be played after the match; Novo Hamburgo won the penalty shootout.
Updated to match(es) played on October 7, 1981. Source: RSSSF.com Rules for classification: 1) points; 2) wins; 3) goal difference; 4) number of goals scored.
Updated to match(es) played on November 29, 1981. Source: RSSSF.com Rules for classification: 1) points; 2) wins; 3) goal difference; 4) number of goals scored.