He told Cheng's wife Selina, son Alpha, and daughter Zilvia that Curtis was "so proud to be part of the force", and was cherished by his colleagues who said he was "nothing but positive".
"Curtis was one of our own, one of our friends. His circumstances are our circumstances.
"The pain and disorientation we feel at Curtis' death is all the more acute as a result."
Cheng was given a posthumous commendation for his service.
"Mr Cheng displayed integrity, loyalty, commitment, professionalism and devotion to duty as a member of the NSW Police Force, and thus is highly commended for his service," the commendation reads.
Alpha Cheng in his eulogy called on mourners to honour his father by following his example.
"Dad did everything in his own, quiet, little way," Alpha said.
"We need to do the little things for the people around us... if we all do that little bit more as dad did in his life, I believe we can live in a more gentle and harmonious world."
Also among the mourners were NSW Premier Mike Baird, Police Minister Troy Grant, NSW Governor David Hurley, Opposition Leader Luke Foley and police representatives from Australia and New Zealand.
Cheng, 58, died after 15-year-old Farhad Jabar shot him as he was leaving work on October 2.
Jabar died after he was shot by police at the scene.
Two men who allegedly helped the 15-year-old Jabar carry out the attack were refused bail in court.
-AAP