The invention aims at providing a marine built-in membrane bioreaction device which is characterized by comprising a reactor, a water inlet and outlet system, an aerating system, a circular grinding system and a charging system, wherein the water inlet and outlet system comprises a buffer tank; sewage to be treated is stored in the buffer tank and enters the reactor through a feed pump; the sewage treated by the reactor is pumped out by a vacuum pump, passes through an ultraviolet sterilization device and is then discharged; the aerating system comprises an aerating pump; the aerating pump is communicated with the reactor through an aerating pipeline; the circular grinding system comprises a circular grinding pump; the circular grinding pump is communicated with the bottom of the reactor through a circular inlet and a circular outlet respectively; large particles and settled sludge at the bottom of the reactor enter the circular grinding pump through the circular inlet and then return to the reactor through the circular outlet; the charging system comprises a charging box; the charging box is communicated with a pipeline between the reactor and the vacuum pump through a charging pump; and the charging box is further communicated with the reactor through the charging pump. The device is small in size, high in sewage treatment efficiency and good in treatment effect.