Rod Stringer was taking nothing for granted against their Essex Senior League opponents as he picked a strong side to take on Barking who were full of confidence being sat top of their league by five points and with three games in hand.
The home side were first to have the ball in the back of the net as Omari Delgado was slipped in by Petrit Elbi, but after Delgado had beaten Ross Fitzsimons his joy was quashed by seeing the linesman's flag up on the far side.
To add to the disappointment of seeing their goal chalked off, just two minutes later the Clarets took the lead when Matt Young's cross from the right was headed past his own goalkeeper by defender Billy Rix after 12 minutes.
Chelmsford looked to be in control from the get go and had deservedly taken the lead, but Barking managed to find an equaliser midway through the half when Jay Taylor got the better of Adam Bailey-Dennis to feed John Bricknell who fired low and hard past Fitzsimons.
Barking were only level for seven minutes though as Chelmsford began scoring almost at will, with Luke Daley putting Chelmsford back in front with a tap in from close range.
Max Cornhill then headed home an Elliot Buchanan corner to put daylight between the visitors, before Daley grabbed his second of the game with a lovely strike from distance which was parried into the top corner by Jack Kelly to make it four.
In the second half Chelmsford continued to push forward for more goals, but Elbi had a great chance for the home side as he rattled the bar early in the half.
City though went straight up the other end to score their fifth of the evening when Cornhill saw Kelly off his line, sending a delightful chip over the stranded goalkeeper for his second of the evening.
Five minutes later Max Porter scored his first for the Club after Young's cross was headed away only as far as Porter, who on the volley found the bottom corner for City's sixth.
And not to be outdone by his cousin John, Billy Bricknell got in on the act just after the hour after he was slid through by Buchanan, finding the back of the net with a low drive.
It was Chelmsford's biggest win in the Essex Senior Cup since a 10-3 win against Billericay in 1993 as they comfortably became the first team to advance to this season's Quarter Finals.
1. Jack Kelly
2. Ben Higgs
3. Ricky Tarbard
4. Jay Taylor
5. Billy Rix
6. Ben O’Brien (C)
7. Joe Staunton
8. Liam Burgess
9. Petrit Elbi
10. Omari Delgardo
11. John Bricknell
12. Paul Oshin (On for Liam Burgess 46’)
14. Joe Pearman (On for John Bricknell 46’)
15. James Peagram
16. Steve Willis
17. Ashley Wackers-Kyriacou (On for Omari Delgado 68’)
1. Ross Fitzsimons
2. Matt Young
3. Daniel Blanchett
4. Max Porter
5. Adam Bailey-Dennis
6. Mark Haines
7. Luke Daley
8. Max Cornhill
9. Billy Bricknell (C)
10. Elliot Buchanan
11. Frankie Merrifield
12. Robbie Willmott
14. Shaun Jeffers (On for Billy Bricknell 82’)
15. Shamir Mullings (On for Frankie Merrifield 67’)
16. Josh Rees
18. Chris Bush (On for Adam Bailey-Dennis 24’)
Barking: John Bricknell 20’
Chelmsford City: Billy Rix O.G. 12’, Luke Daley 27’, 34’, Max Cornhill 31’, 53’, Max Porter 58’, Billy Bricknell 64’
Chelmsford City: None
City Man of the Match: Luke Daley