The hosts took the lead in the first half when Paul Caddis's looping cross found striker Alan Connell who headed past Bees keeper Dean Brill.
Wes Fotheringham denied Sam Deering and Ricky Holmes a second-half equaliser for Barnet, who had Charlie Taylor sent off late on for fouling Oliver Risser.
League Two title chasers Swindon face League One's Chesterfield in the final.
The match on 25 March will be the fifth Wembley final in Swindon's history, and manager Paolo di Canio celebrated with fans, who came on to the pitch after victory over Barnet was secured.
Di Canio's side outclassed the visitors in the first half but it was Barnet who went close early on when Holmes' swerving effort from Mark Byrne's cross hit the side netting.
The Robins powered forward and Caddis's delivery found Connell, who headed home with less than a quarter of the game gone.
Swindon continued to dominate, with Paul Benson twice being denied from close range by Brill, while Raffaele de Vita failed to finish following a blistering run.
The Bees found their stride after half-time but failed to make the breakthrough with Deering's swerving shot from 25 yards their best effort.
Substitute Taylor's high challenge on Risser earned him a straight red and Swindon held on.

LINEUP, BOOKINGS (7) & SUBSTITUTIONS (6)

Swindon Town

  • 35 Foderingham
  • 03 Kennedy Booked (Murray - 82' )
  • 05 Devera
  • 07 Caddis
  • 08 Ferry (Risser - 58' Booked )
  • 10 Ritchie
  • 12 McCormack
  • 24 Smith
  • 09 Benson
  • 17 Connell
  • 23 De Vita (Cibocchi - 77' )

Substitutes

  • 26 Smith
  • 27 Cibocchi
  • 13 Risser
  • 29 Magera
  • 34 Murray

Barnet

  • 01 Brill
  • 05 Dennehy Booked
  • 17 Hector
  • 19 Saville Booked
  • 21 Kamdjo (Obita - 58' )
  • 30 Downing
  • 04 Hughes Booked
  • 08 Byrne (Taylor - 74' Dismissed )
  • 10 Deering (Mustoe - 90' Booked )
  • 11 Holmes
  • 23 McLeod

Substitutes

  • 18 O'Brien
  • 12 Mustoe
  • 16 Hajrovic
  • 37 Obita
  • 24 Taylor
Ref: Deadman
Att: 10,406

MATCH STATS

Possession45%55%97minsSwindon TownBarnet

Shots

146

On target

72

Corners

62

Fouls

412

Live Text Commentary

90:00+5:06
The referee blows for the end of the match.
90:00+4:37Booking
BookingBooking for Oliver Risser.
90:00+2:41
Paul Benson is ruled offside. Dean Brill takes the free kick.
90:00+2:00
Shot by Ronan Murray from 18 yards. Paul Downing gets a block in. Short corner worked by Matt Ritchie.
90:00+1:17
Paul Caddis takes the free kick.
90:00+1:17Booking
BookingBooking for Jordan Mustoe.
90:00+1:10
Free kick awarded for a foul by Jordan Mustoe on Matt Ritchie.
89:32Substitution
SubstitutionJordan Mustoe replaces Sam Deering.
87:01
Short corner worked by Alessandro Cibocchi.
85:26
Direct free kick taken by Alan McCormack.
85:26Dismissal
DismissalThe referee sends off Charlie Taylor for violent conduct.
85:14
Free kick awarded for an unfair challenge on Oliver Risser by Charlie Taylor.
83:26
The referee gives a free kick against Izale McLeod for handball. Wesley Foderingham takes the indirect free kick.
82:15
Charlie Taylor challenges Alan McCormack unfairly and gives away a free kick. Free kick taken by Wesley Foderingham.
81:06Substitution
SubstitutionRonan Murray is brought on as a substitute for Callum Kennedy.
81:06
Izale McLeod has an effort at goal from outside the box which goes wide left of the target.
80:03
Direct free kick taken by Michael Hector.
80:03Booking
BookingCallum Kennedy receives a caution.
79:45
Free kick awarded for an unfair challenge on Mark Hughes by Callum Kennedy.
79:10
Alessandro Cibocchi takes a outswinging corner from the left by-line to the near post, clearance made by Ricky Holmes
.