The invention discloses a two-stage treatment wet desulphurization method for high-sulfur coal-fired flue gas. In the method, a horizontal flow absorption tower, a reverse flow spray absorber, an oxidation blower, a stock tank, a stirrer, a plaster discharge pump, an oxidation spray gun, a circulating slurry pump, a mechanical demister, and a spray layer device are arranged. Flue gas from a draught fan passes through the conventional flue, enters the horizontal flow absorption tower to be subjected to first-stage treatment, is washed, and enters the reverse flow spray absorber to be subjected to second-stage desulphurization; and the purified flue gas passes through the demister and is discharged through a chimney. The method is suitable for treating high-sulfur coal-fired flue gas, and has the characteristics of small occupied area, low investment, high desulphurization efficiency, low energy consumption, stable operation and the like.