The utility model discloses a main part membrane fermentation vat, including the fermented passageway of main part membrane constitution the feed mechanism that main part membrane one end was provided with and the fermentation passageway communicates the main part membrane other end is installed the membrane and is covered the top interval of fermentation passageway is provided with a plurality of bacterial shower heads, installs the bacterial back flow in the bottom of fermentation passageway. Among the prior art, the construction of big -and -middle -sized fermentation vat need be carried on busy at putting up installationsly usually, consumes a large amount of concrete, reinforcing bar and other assistance materials promptly to require ambient condition and geological conditions very high, make the fermentation vat to establish the cost huge, the utility model discloses during the installation, can on dry river course, level land or the foot of the hill department of repairing a little builds, utilize the main part membrane of specialty as the carrier of fermentation, arrange conveniently and carry that even change at the fermentation vat and move the back, the main part membrane can take out used repeatedly, greatly reduced the construction cost of fermentation vat.