Abstract: A low-noise car trunk reducer which includes an internal gear housing, an input mechanism, and at least two stages of planet gear transmission mechanisms; the internal gear housing includes an internal gear housing body and a first helical gear integrally formed on an inner wall of the internal gear housing body; a first-stage planet retainer of the first-stage planet gear transmission mechanism is formed integrally; the input mechanism includes a first-stage sun gear; the first-stage sun gear, the first-stage planet gear, the second-stage sun gear, the second-stage planet gear and the internal gear housing body are all transmitted by helical gears.