An incident packed opening half could have gone either way but it was Ruthin who took control after the break to run out 4-1 winners.
The visitors were ahead after just three minutes as Mike Garrod got behind the home defence to score and a minute later Glan keeper Marc Newbould did well to save from Gwydion Ifan.
The Bodorgan boys came close to levelling on 9 minutes as a great ball in from Anthony Hughes was flicked goalwards by Kevin Roberts, the ball clipping the crossbar.
The visitors threatened again a minute later as Newbould again had to be alert to save from Ifan then the Glan keeper pulled off a tremendous save from Garrod as he threw himself to his left to just get his fingertips to the ball and push it for a corner.
Ruthin went further ahead in the 19th minute as Bryn Jones failed to clear a right flank cross and Ifan was there to take advantage but again Glan came back strongly with James Burgess only a foot off target following a misskick from Ruthin keeper Dylan Jones.
On 25 minutes there was renewed hope for the Anglesey side as Anthony Hughes was fouled by the keeper and Kevin Roberts easily converted the spot kick but within two minutes Ruthin had regained a two goal lead as Gareth Owen headed a right wing cross into his own goal.
From the kick-off Glantraeth were quickly back on the attack and were awarded another penalty after Anthony Hughes was tripped but this time keeper Dylan Jones guessed right and dived to his right to save.
It was action packed stuff with chances coming at both ends with Glan coming close to scoring again as a volley from Gareth Owen came back off the crossbar then on the stroke of half-time Kevin Roberts struck a free kick inches wide with Dylan Jones well beaten.
The second period was a tame affair after the earlier thrills with Ruthin, playing with a strong wind at their backs, taking control and Glan struggling to make meaningful progress.
Tom Daulby missed a great opportunity for the visitors in the opening minute of the half, skying the ball after good work by Garrod and it took another fine save from Newbould on 52 minutes to prevent Dafydd Jones adding to Ruthin's tally.
Glantraeth came closest on the hour mark as Anthony Hughes, who was constantly probing for openings, cut in from the left but his cross was blocked and the danger cleared and as play switched to the other end Ruthin were awarded a corner on the right from which Garrod rose to head home.
It was all but over as a contest and it was the visitors who came closest to adding to the scoreline as time was played out with Will Roberts clipping the bar on 63 minutes and Newbould pulling off another tremendous save with five minutes remaining, this time from substitute Jonathan Prosser.
Glantraeth: Marc Newbould, Bryn Jones, Caerwyn Roberts, Danny Wade, Gareth Owen, Mark Owens, Anthony Hughes, Emyr Rowlands, James Burgess, Kevin Roberts, Chris Evans.