A U-shaped floor level-molding device having a rubber strip-based contraction-expansion structure comprises: a U-shaped floor level-molding device (10); and multiple room molds (30). The U-shaped floor level-molding device (10) comprises: a bearing body (11) provided with multiple support plates (111) spanning over the bearing body (11). Each support plate (111) is connected and fixed to multiple lifting rods (1111). Multiple longitudinal flow paths (31) communicating with each other are formed between adjacent room molds (30). Top portions of respective room molds (30) are fixed to and lifted by respective lifting rods (1111). Multiple flexible rubber strips (61) are embedded in grooves (33) at bottom sides of the respective room molds (30). The structure can achieve a satisfactory sealing effect.
