The Robins reached 92 points with their 27th league victory of the season at Valley Parade thanks to James Tavernier's brace and further goals from Joe Bryan, Luke Ayling, Aden Flint and Aaron Wilbraham.
Tavernier, who went up as a Rotherham player out of League One last year, fired in the opener after his initial effort was blocked before Bryan jumped highest to double Bristol City's advantage.
Ayling's fortuitous effort made it 3-0 after the break, Flint then headed a free-kick home, Tavernier stabbed in his second and Wilbraham rolled home a sixth to seal victory and promotion.
Source : PA
Source: PA