The invention relates to a film forming method for a biological carrier in an internal circulation bioreactor. The film forming method comprises the following steps of: adding the needed biological carrier into the internal circulation bioreactor by 2 to 5 times; every time after a biological filler is added, introducing air to make the biological carrier in a fluidized state; adding domesticated inoculation active sludge into the bioreactor in a spraying way; after spraying, ventilating for 6 to 72 hours; discharging the sludge; and culturing in a continuous water feeding way. In the method, needed starting power is low, film forming time is short and a formed biological film has high impact load resistance.