Egypt, who last won the tournament in 2010 and lost in the 2017 final, secured their second win in two matches to move on to six points and guarantee a top-two finish in Group A.
DR Congo could have had a chance to take the lead but Marcel Tisserand’s effort hit the woodwork.
Egypt took the lead in the 25th minute when Salah’s cross was met by Aston Villa’s Ahmed Elmohamady, who finished at the second attempt.
Jonathan Bolingi then came close to equalising for Congo but the woodwork came to Egypt’s rescue again.
Liverpool forward Salah then added a second in the 43rd minute with a powerful strike when surrounded by two DR Congo players after a fine run from Trezeguet.
In the 2nd half, Yannick Bolasie nearly pulled a goal back late on for the visitors but curled a free-kick just wide.
Egypt will face Uganda in the last group game while Congo will play Zimbabwe.