The invention discloses a composite gasoline fractionating tower of an ethylene device. A gasoline separating segment, a diesel oil separating segment, a medium oil circulating segment, a quenching oil circulating segment and a pyrolysis gas feeding segment are sequentially arranged in the fractionating tower from top to bottom; the gasoline separating segment is provided with an orifice flow-overflow composite groove-type liquid distributor and efficient ring rectangular saddle packing; the diesel oil separating segment is provided with a thermal compensation type oil collecting tank, an orifice flow-overflow composite groove-type liquid distributor and hyperbolic corrugated tower discs; the medium oil circulating segment is provided with a variable-cross-section variable-aperture tubular liquid distributor, hyperbolic corrugated tower discs and a thermal compensation type oil collecting tank; the quenching oil circulating segment is provided with a variable-cross-section variable-aperture tubular liquid distributor and a herringbone baffle with holes; the pyrolysis gas feeding segment is provided with a circulation feeding distributor without a flow guiding plate and a liquid-trapping energy absorber. The gasoline fractionating tower is high in throughput, low in pressure drop and capable of resisting blocking and has the advantages of being high in operating flexibility, good in separating effect, excellent in heating effect, high in anti-blocking property and the like, and long-period stable operation of the device is guaranteed.