PSG was five-time defending champion when it was beaten by eventual runner up Guingamp in the quarters last season, but Thomas Tuchel's side had little trouble in progressing to its first final of the season on Thursday (AEDT).
Having had to wait until late on in its scrappy Coupe de France win over Lorient on Monday (AEDT), PSG had things far easier from the off thanks to Marquinhos' early header.
Ghislain Konan's own goal doubled PSG's tally, with Marshall Munetsi's red card reducing Reims to 10 men before substitute Nianzou Kouassi bundled in the capital club's landmark competitive goal to wrap up the win in style.
Having made a vital last-ditch block as PSG withstood some early pressure, Marquinhos made his mark at the other end in the ninth minute, rising highest to head home Neymar's cross.
Kylian Mbappe wanted a penalty moments later, though referee Mikael Lesage rightly judged Reims goalkeeper Predrag Rajkovic to have made no contact.
PSG had their second just after the half hour – the unfortunate Konan only able to divert Neymar's brilliant free-kick into his own side's net.
Chasing a club record, Neymar curled wide from the edge of the box on the hour, though Keylor Navas had to keep out Boulaye Dia's effort soon after, with PSG then losing Marquinhos to injury.
Reims' task was made tougher when Munetsi was sent off for a lunge on Marco Verratti, however, and it was Marquinhos' replacement Kouassi who was on hand to deal the final blow from close range after Rajkovic repelled Leandro Paredes' volley.
With tempers boiling over, Rajkovic was fortunate not to join Munetsi in seeing red when he lashed out at Mbappe as PSG cruised into the final.