Los Blancos had to come from a goal down to beat Real Sociedad 4-1 at the Santiago Bernabeu in La Liga on Saturday, stretching their lead at the top of the table to eight points.
First half goals from Eduardo Camavinga and Luka Modric cancelled out Mikel Oyarzabal's opener for the visitors before Karim Benzema and Marco Asensio added two more after the break.
Real Madrid go into Wednesday's game with a 1-0 deficit, having lost the first leg in Paris three weeks ago but Ancelotti is confident qualification to the quarterfinals will be on the cards if the performance against Sociedad is replicated.
He said: "We played really well from the beginning. The plan was to press up front, to stop Real Sociedad building attacks from the area. It worked.
"The physical effort was huge, we did well. If we play like this on Wednesday, we have a bigger chance of going through."
"It was an important match because we had the opportunity to take advantage in LaLiga," he added, alluding to Sevilla's 0-0 draw with Deportivo Alaves on Friday.
"The team has understood very well the importance of the match. It is a match that gives us great hope.
"This is the intensity that we have to have and that the fans like. It can be repeated on Wednesday against PSG.
"All of Madrid believes more after this game. The idea of going out [to show their appreciation for the supporters] at the end of the game came from the players, because on Wednesday the help of the fans is essential."
