A desulfurization and denitration integrated device comprises a top bin (1), a shell (2), an ammonia spraying master pipe (29), a denitration chamber (5), a smoke inlet (22), a smoke discharging port (34), a discharging valve (18) and a support (35), wherein the shell is divided into an upper denitration region, a middle buffering region and a lower desulfurization region through upper and lower annular partitioning plates (10), the denitration region and the desulfurization region are cut into different chambers through inverted truncated hollow cones (3) and truncated hollow cones (4), and a purified smoke outlet chamber (33), the denitration chamber (5) and a denitration smoke inlet chamber (6) are sequentially arranged in the denitration region from outside to inside; a desulfurization smoke inlet chamber (24), a desulfurization chamber (13) and a desulfurization smoke outlet chamber (14) are sequentially arranged inside the desulfurization region from outside to inside; the desulfurization chamber (13) and the denitration chamber (5) are communicated through discharging pipes (9) in the buffering reigon, and the desulfurization smoke outlet chamber (14) and the denitration smoke inlet chamber (6) are communicated through an eddy ammonia mixing chamber (25) in the buffering region.The occupied area is small, smoke flow is distributed reasonably, the quantity of filled purifying agent is small, and desulfurization and denitration efficiency is high.