The invention discloses an oxidation ditch tandem arranged desulfurization tower which comprises a desulfurization front tower and a desulfurization back tower. A smoke outlet of the desulfurization front tower is communicated with a smoke inlet of the desulfurization back tower, and lower slurry outlets of the desulfurization front tower and the desulfurization back tower are communicated through an oxidation ditch. The invention further discloses a desulfurization system which comprises the oxidation ditch tandem arranged desulfurization towers and further comprises a first slurry circulating pump, a first oxidation air tube, a second slurry circulating pump, a second oxidation air tube, an oxidation fan and a slurry discharge pump. In the oxidation ditch tandem arranged desulfurization tower and the desulfurization system using the desulfurization tower, bottoms of the two desulfurization towers are communicated through the oxidation ditch, water and materials which pass in and out the desulfurization towers are converged in the oxidation ditch, so that slurry can be adjusted in the oxidation ditch, water and material balance of the desulfurization system and the signal desulfurization tower can be easily controlled, control is simple, SO2 in smoke can be absorbed through the two tandem desulfurization towers, and desulfurization efficiency is high.