Scott Murray's 26th goal of the season after 31 minutes and Lee Peacock's scrambled follow up 12 minutes ensured Bristol City go into their play-off campaign on a high.
Vale fashioned some neat raids from mid field but this counted for little as Murray started and completed the move for his latest goal,stretching past defenders to reach Matt Hill's low return cross.
The ball for the second also came in from the left, Bell this time the provider. Peacock got the vital touch after his initial effort had come back off keeper Mark Goodlad.
Previous to those strikes Mickey Bell had hit the side netting while Peacock skimmed a header off target.
Vale began the second half brightly and carried the game to City for the opening 20 minutes of the second half, Adrian Littlejohn going close.
However, City soaked up the pressure to run out comfortable winners, threatening to extend their lead as youngster Leroy Lita fired in three sharp shots on target.