The invention discloses a flow crossing-baffling composite gasoline fractionating tower of an ethylene device. Micro baffling plates which are arrayed in an interlaced manner are arranged in parallel up and down at a quenching oil circulating section, and a vertex angle of each micro baffling plate is within 90 to 139 DEG; symmetrical bevel edges at the two sides of the vertex angle of the baffling plate are provided with symmetrical vertical folded edges; flow-crossing sieve plates with the diameter of sieve holes within Phi18 to 24mm are arrayed up and down at a medium oil circulating section; flow-crossing sieve plates with the diameter of the sieve holes within Phi13 to 24mm are arrayed up and down at a diesel oil separating section; and flow-crossing sieve plates with the diameter of sieve holes within Phi13 to 18mm are arrayed up and down at a gasoline separating section. The gasoline fractionating tower of the invention overcomes the problem of polymer blockage frequently occurring in the present plate-type fractionating tower and has the remarkable advantages of strong impact and vibration resisting capability, low tower pressure, high ethylene yield, obvious energy saving effect and long-term stable running.