NOVELTY - A combined biogas tank comprises upper tank (1) and lower tank (2) which are connected to lock bolt through locking hoop (6). Feed pipe and the slag discharge pipe are respectively mounted on two sides of lower tank. A tank opening is located on top of the upper tank and has tank cover and groove. One side of the groove has air pipe having an air switch, and another side of the groove has biogas output pipe that is connected to biogas master switch (9). The lower tank s equipped with anti-floating fence (13) to immerse fodder in the liquid dung.    USE - A combined biogas tank for use in generating biogas useful in rural areas.    ADVANTAGE - The biogas tank may be conveyed in a convenient manner; has fine seal effect and long service life; and solves the problems of the biogas tank used in rural which has poor stability, erosion resistance, short service life, poor sealing effect and no coldness-resistant ability and which influences fermenting of anaerobic bacteria and generation of biogas. The reactor connects all biogas tanks that solves problem of gas interruption caused by feeding or cleaning biogas tank which influence the regular service.    DETAILED DESCRIPTION - A combined biogas tank comprises upper tank having tank opening on its top; lower tank having anti-floating fence to immerse fodder in the liquid dung. The upper and lower tanks are connected to lock bolt through locking hoop (6). Feed pipe and the slag discharge pipe are respectively mounted on two sides of lower tank. The tank opening has tank cover and groove. One side of the groove has air pipe having an air switch, and another side of the groove has biogas output pipe that is connected to biogas master switch. The biogas output pipe is equipped with user connection pipe and biogas tank connection pipe. The biogas tank connection pipe is connected to connection pipe switch. The feed pipe is equipped with soil pipe and pipe cover. The slag discharge pipe is equipped with pipe cover.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic drawing of the combined biogas tank.    Upper tank (1)    Lower tank (2)    Locking hoop (6)    Biogas master switch (9)    Anti-floating fence (13)