The invention discloses a displacement adjusting and compensating device as well as a rail system comprising the displacement adjusting and compensating device. The displacement adjusting and compensating device comprises a first supporting part and a second supporting part; the displacement adjusting and compensating device is characterized in that axial movement can occur between the first supporting part and the second supporting part, wherein the first supporting part comprises an upper accommodating space and a lower accommodating space; the upper accommodating space is used for accommodating a filler; the lower accommodating space is used for being embedded into the second supporting part; and the upper accommodating space and the lower accommodating space are connected through an opening, and the size of the opening is determined in a manner that the filler can pass through.