The invention relates to a modular biological sewage treatment device and process. The modular biological sewage treatment device comprises a tank body, macro-pore carrier filler and immobilized microorganisms thereof, a water inlet pipe, a water outlet pipe, an aeration pipe, a filter screen and an effluent weir. The device can be demounted, assembled and serially combined into different macro-pore carrier immobilized microorganism-biological aerated filter (IBAF) sewage treatment bed types. The device and the IBAF sewage treatment process thereof have the advantages that the device is large in organism capacity, even in water distribution, good in impact load resistance, high in sewage treatment efficiency, good in discharged water quality and the like, and automatic control and detection can be achieved by the aid of the industrial control technology; the device is simple, small in floor space, low in investment, high in treatment efficiency, low in energy consumption and suitable for the treatment and recycling of various sewage and especially high-concentration organic sewage high in ammonia and nitrogen content.