The invention relates to a device for separating rough styrene contained in pyrolysis gasoline, comprising a rectifying tower, partition walls (7, 8), a liquid distributor, a condenser, a tower-top product buffer tank, liquid collectors (15, 16) and a reboiler, wherein the two partition walls (7, 8) divides the rectifying tower into six parts, i.e. a public rectifying area, a feeding area, a C6-C7 discharging area, a steam stripping area, a rough styrene discharging area and a public stripping area; a partition wall segment is from the top end of the partition wall (7) to the bottom end of the partition wall (8); the top of the public rectifying area is provided with a temperature measuring instrument, and light component C5 fractions are extracted in the public rectifying area; the left side of the partition wall (7) is provided with the feeding area, materials enter from the feeding area, the right side of the partition wall (7) is provided with the C6-C7 discharging area, and the C6-C7 fractions are extracted in the C6-C7 discharging area; the left side of the partition wall (8) is provided with the steam stripping area, and the right side of the partition wall (8) is provided with the rough styrene discharging area; heavy component C9 fractions are extracted in the bottom of the public stripping area, and the bottom of the public stripping area is also provided with the temperature measuring instrument. The invention saves two towers and corresponding accessory equipment due to the rectifying tower with the partition walls (7, 8) and saves the energy by more than 30 percent.