The first half was largely a non event.
Matt Ritchie's shot inside the first 30 seconds was the closest either side came to scoring, but his 25-yard drive was well saved by Exeter goalkeeper Ben Hamer.
Matt Taylor headed onto the roof of the net as Exeter started the second half well, while Alan Sheehan brought a fine save from Hamer with a free kick from 25 yards for the troubled Robins.
Exeter broke the deadlock with 11 minutes remaining when Calvin Andrew handballed Billy Jones' corner kick inside the penalty box. A penalty was awarded and Harley rolled the ball down the middle of the goal as David Lucas dived to his right.
Swindon responded with Andrew firing wide shortly after Harley`s goal, but that was as good as it got for the Robins, who on this form look certainties for relegation to League Two.
Exeter 1-0 Swindon: Match Report - view commentary, squad, and statictics of the game as it happened.