The invention discloses a heat recovery unit for engine waste heat generation ORC (organic Rankine cycle) systems, which comprises a first-stage high-temperature waste heat recoverer, a second-stage waste heat recoverer, a metal connecting pipe and flanged corrugated pipes, the metal connecting pipe is between the two stages of waste heat recoverers, and the flanged corrugated pipes are located on both ends and connected with engine tail gas exhaust pipes. By adopting the high-efficiency compact automobile heat exchanger enhanced heat transfer technique and combining with the characteristic of engine tail gas that carbon can be easily deposited to cause blockage, the invention designs the unit with the two stages of engine tail gas heat absorbers, consequently, the heat of high-temperature engine tail gas can be efficiently absorbed and utilized by an engine waste heat generation ORC system, and coolant decomposition which takes place when the heat of high-temperature tail gas is absorbed by coolant as working medium in the ORC system is prevented.