The present invention provides an assembled subway station and a construction method thereof, and relates to the field of subway stations. The assembled subway station comprises a plurality of members assembled in a ring shape, the plurality of members being a bottom plate member, a bottom corner member, a side wall member, a middle plate member, a top corner member, and a top plate member, and the edges of each member are respectively provided with a concave-convex structure that matches with each other, and the butt joints of the two neighboring members are filled with a sealing structure; and the edges of each member are also provided with an embedded groove that extends in the longitudinal direction, and the embedded grooves of the two neighboring members are set relative to each other and are installed with a connection member for forming a counter fastening force on the two neighboring members. The edges of the respective members are also provided with longitudinally extending insert slots, the insert slots of the two adjacent members are provided opposite to each other and therein are mounted a connection member for forming an opposing fastening force on the two adjacent members. Through the connection to the two adjacent members to form the opposite fastening force, to ensure that the sealing structure at the docking place can play a better sealing effect; from the complete connection instead of a plurality of bolts structure, to withstand the bending moment is greater and uniform force transmission, can form a more reliable fastening force to the two adjacent members, to meet the high-performance waterproofing requirements, to simplify the operation, and to improve the efficiency of the construction.