Provided are an earth tunnel modular supporting structure and a construction method thereof. A metal tool bit is firstly jacked to a preset position, and then pipe sheet are jacked in the direction ofthe tool bit; a core soil retaining excavation method is used for gradual excavation until the tunnel design length is reached; the tool bit is recycled; binding hol and a grouting holes are formed in the pipe sheets, prestressed tendons are arranged in the binding holes, grouting pipes are arranged in the grouting holes in the adjacent pipe sheets connected in the same direction, and rubber water check rings are arranged between the grouting holes and the grouting pipes; and overflow holes are formed in the grouting pipes, and the reinforcing area is widened. According to the earth tunnel modular supporting structure and the construction method thereof, a protection structure of enough strength can be provided before excavation, friction between the pipe sheets and a soil layer during section-by-section jacking is reduced, the loss of a jack is reduced, and construction energy consumption is reduced. The pipe sheets are spliced through rabbet joints, and cross joints are completely eradicated; and the rubber water check parts are arranged, so that the waterproof effect of the supporting structure is improved. The annular constraining force part is provided by surrounding soil, and used reinforcing steel bars are reduced. The method has the characteristics of being safe, efficient and saving.