The utility model relates to the technical field of oil-gas field development and particularly to an assembling tank. The assembling tank comprises a tank wall and bag bodies of which the upper ends are open; the tank wall is formed by splicing at least two wall boards; the bag bodies are positioned in the tank wall; and the upper ends of the bag bodies are fixed on the edge of the upper end of the tank wall. The assembling tank has a reasonable and compact structure and is convenient to use; the tank wall is formed by splicing a plurality of jointed boards and the bag bodies are laid in the tank wall; and the assembling tank can be rapidly installed, meanwhile, is convenient to disassemble and tranship, can be repeatedly utilized, has a short construction period, is low in cost and has good sealing performance. Reinforced concrete is not needed, resource waste is reduced, construction and maintenance cost is reduced, the environment is protected and the economic benefits and the social benefits of production are improved.