The Saints led from the moment Ben Martin headed home Lee Chappell’s corner on 11 minutes and they never looked back.
Four second half goals, two for Louie Theophanous and two for Junior Morias, cemented the win that keeps City in the league play-off places.
Having won 5-1 away at Bishop’s Stortford in the last game, City were back among the goals early in this encounter.
Direct running from winger Shaun Lucien won a corner and from the right skipper Chappell lofted in a set-piece which central defender Martin rose highest to meet and plant past keeper Tom McHale.
Midway through the half there was concern for the hosts as striker Sam Merson clashed heads with Truro defender Arran Pugh.
The Saints man stayed down and was briefly put in the recovery position, before sitting and then being led off the field.
Truro offered little threat going forward, they did force three corners in succession before the break, but did not worry home keeper James Russell.
Four minutes into the second half the hosts doubled their advantage.
Left back Tom Bender drilled the ball into the box to the feet of Theophanous, he found space to turn and fire a low effort into the back of the net.
Saints should have been 3-0 ahead when they broke following a Truro corner.
Lucien charged forward from his own half with the ball, beat a defender, but from inside the Truro box pulled his shot wide.
A third did come though as Lucian crossed for Morias, his shot was parried by the keeper Tom McHale, the ball was collected by Theophanous who rifled in.
With 10 minutes to go Saints hit a fourth as substitute Morias side-stepped his way through the tiring visiting defence to net.
In added on time Morias completed the rout tapping into an empty net after Rhys Hoenes’ cross from the right beat McHale.
The three points see Ian Allinson’s St Albans side fourth in the table.
City face London Colney on Monday at Clarence Park in the Herts Senior Cup before they welcome Carlisle on Saturday in the FA Cup.