A serially-connected type wastewater biochemical treatment device comprises multiple fermentation tanks (15) in a serial connection. An aerating and stirring device (21) is disposed in any one of the fermentation tanks (15), and biochemical beds (20) are disposed in other fermentation tanks (15). Each aerating and stirring device (21) comprises an inner nozzle (2) and an outer nozzle. The outer nozzle is formed by sequentially connecting a mixing chamber (3), a reducing section (4) and a diffuser (5) from the top to the bottom. The inner nozzle (2) is axially inserted into the outer nozzle from the upper end of the mixing chamber (3). The upper end of the mixing chamber (3) is located in the inner nozzle (2), and a plurality of air intake holes (1) is disposed around the upper end of the mixing chamber (3). A stirring blade (7) is disposed outside the diffuser (5), a dome (8) is disposed on the periphery of the stirring blade (7). The adjacent fermentation tanks (15) are connected by using overflow pipes (18), and the heights of the overflow pipes (18) of the adjacent fermentation tanks (15) gradually decrease. A hollow fixing shaft (6) is connected to the upper end of the inner nozzle (2). A rotary joint (13) is connected to an upper opening of the fixing shaft (6). The rotary joint (13) is connected, by means of a circulating pump (19), to the fermentation tanks (15) in which the biochemical beds (20) are disposed. In the device, when a great amount of oxygen is dissolved into wastewater during the stirring, oxygen is provided to biochemical bacteria. The serially-connected type wastewater biochemical treatment device can be used in treatment of domestic wastewater.
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