Routledge was sent off for his reaction to a strong tackle from Karl Henry in the 86th minute of the 1-1 draw, with Henry booked for the challenge.
The dismissal had left Routledge facing a three-match ban but that has been lifted after his appeal was upheld.
A Football Association statement said: "Following an Independent Regulatory Commission hearing on Friday 2 January 2015, Swansea City's Wayne Routledge has had his claim for wrongful dismissal upheld.
"Routledge was dismissed during his side's 1-1 draw against Queens Park Rangers on New Year's Day for violent conduct.
"The three-match suspension has therefore been withdrawn with immediate effect."
Routledge's red card was one of a number of decisions from referee Anthony Taylor which upset Swansea - as QPR goalkeeper Rob Green should have been sent off for handling outside his area early in the match
Swans boss Garry Monk described Henry's challenge on Routledge as a "leg-breaker" and said the officials were mistaken in believing Routledge had kicked out in response.
"It's a leg breaker," Monk said
"I think everyone knew in the stadium apart from the official and then the double whammy of our player getting sent off for apparently kicking out.
"He doesn't kick out at all
I just hope justice is done not just for us but for football in itself.
"I'm losing a bit of faith
It's hard for us to keep faith when we continually have decisions like this, big moments within games.
"That sounds like me moaning, I'm not at all
I'm just telling you the facts.
"I hope the red card gets rescinded because that will 100 per cent be the right thing to happen.
"We'll be appealing for sure
My player goes from nearly having his leg broken to getting sent off, I don't see how that can happen."
Despite the red card, Swansea mustered a stoppage-time leveller through Wilfried Bony, cancelling out Leroy Fer's strike for the hosts.
Source : PA
Source: PA