The Spanish striker has made seven first-team appearances and scored twice, one of which came just a minute after being sprung form the bench against Athletic Club last season.
Guiu has also been linked with Bayern Munich and Sevilla, with his release clause set at just €6 million (£5m).
But the Blues were said to be in “advanced talks” with the representatives of the 18-year-old, as reported by The Athletic on Tuesday morning.
Barcelona are still hoping to convince the teenager to sign a new deal to keep him at the club, but Chelsea appear to have the upper hand after speaking to his representatives “on more than one occasion”.
Transfer expert Fabrizio Romano claims that the west London outfit are approaching the “final stages” of their approach for Guiu and plan on triggering his release clause once personal terms are agreed.
Romano previously reported that Chelsea were leading Bayern in the hunt for Guiu after presenting a “specific project for his development at the club”.
The Athletic say that the player will not be loaned out to sister club Strasbourg, which is also owned by Todd Boehly, and will be a part of the first-team squad next season if he moves to Stamford Bridge.
Meanwhile, Chelsea are set to send youngster Alfie Gilchrist out on loan next season. The 20-year-old has received interest from Serie A side Como, who are managed by Cesc Fabregas, and Championship outfit Preston North End.
The defender made 15 appearances in all competitions after making his Premier League debut last season.
