The utility model provides an absorbent composite module formula air filtration system of secondary is prevented to online deashing, includes multiunit modular filter unit, modular filter unit includes filtering framework, filter core, ash removal device, connects grey device, modular filter unit is equipped with a plurality of layers, the filter core both sides are equipped with the filter core baffle, modular filter unit one side is equipped with horizontal deashing sealing door module, horizontal deashing sealing door module includes the maintenance door of system, pedestrain passage frame and walking platform, and pedestrain passage frame one side is equipped with rain -proof cover, and pedestrain passage frame opposite side is equipped with the sealing door guide rail, and translation sealing door is connected to the sealing door guide rail, is equipped with the module shrouding on the pedestrain passage frame. The problem of appear the dust secondary behind the self -cleaning formula filtration system deashing of pulse and adsorb is solved, have the characteristics that improve pulse deashing effect and filter core performance, and seal single or a plurality of filter module and carry out independent deashing on line, structurally realize through forming single or a plurality of sealed cavities that filter module keeps apart, effectively avoid the secondary absorption behind the deashing.