The 36-year-old will break Ryan Giggs's record of 632 Premier League appearances should he feature for the Baggies against Arsenal on Monday night.
Barry has enjoyed a fruitful 19-year career in the English top flight, having also represented Aston Villa, Manchester City and Everton, as well as winning 53 England caps.
Speaking to the media on Thursday, Barry told reporters: "When I think back to my debut, playing that first game, to hitting this number I am about to reach now, everything has gone so quick in between. It is certainly something, when I do end up finishing, I will sit back and be really proud of, and try to take in what has happened in between a bit more.
"You hit certain landmarks along the way, your 100th and so on but, even when I played 500, I am thinking, 'you are coming towards the end of your career'. You are not expecting to play that many more games after that, so I am really proud to have been able to keep going.
"I want to go as long as possible. Any ex-players and all my family say 'play as long as possible because there'll be plenty of time to sit back and do different things.'"
Barry also holds the record for Premier League yellow cards, with 119, with Wayne Rooney the only other player to have hit 100.