PSG are tipped as one of the favourites to win the competition after the arrival of Lionel Messi but Pochettino said Chelsea's spending makes them the most dangerous team.
"It's possible that Chelsea and ourselves are the two teams to beat on paper, looking at our squads, but Chelsea are the holders so they're the team to beat especially after strengthening their squad," Pochettino told a news conference on Tuesday.
"We're not a team yet. We are a club that has recruited many players this summer. There are some big names but we have to turn into a team. We know that we'll be judged at the end of the season on our results. The pressure is there for all the clubs and we know that for a number of years, the Champions League is PSG's main objective."
Chelsea re-signed Romelu Lukaku for a club record fee of £97.5 million and Saul Niguez on loan from Atletico Madrid, while PSG signed Messi, Georginio Wijnaldum, Gianluigi Donnarumma, Sergio Ramos on free transfers.
Pochettino also added that it is "possible" that Messi, Neymar and Mbappe could start together for the first time on Wednesday.
PSG captain Marquinhos also said that if three forwards do play, the team need to perform as a defensive unit.
"If the three of them are up front, they're experienced players, they know we have to be compact and defend together, and we know the defence has to play high to put them in the best conditions," he said.
"If there's anything to be said I'll certainly say it."
Information from Reuters was added to this report.