The utility model discloses a system for preparation alkene and aromatic hydrocarbon, this system includes: processing unit has low order coal entry, gives birth to lime inlet and mixes the pelletizing export in advance, the pyrolysis device has mixed pelletizing entry, the export of pyrolysis oil gas and the export of pyrolysis solid, the calcium carbide smelting device has pyrolysis solid inlet port, tail gas export and the export of liquid carbide, desulphurization unit has pyrolysis oil gas entry, exhaust gas inlet and the export of desulfurization gas, is advantaged by simple whole structure, low manufacture cost, therefore, the clothes hanger is strong in practicability, and easy popularization.