The invention discloses a shield tunnel segment structure and a connecting structure thereof. The shield tunnel segment structure comprises a segment body and is characterized in that the segment body is mainly composed of a steel plate layer, a concrete layer wrapping the steel plate layer, and steel mesh reinforcements which are located on the two sides of the steel plate layer correspondingly and embedded in the concrete layer; the lateral edges of the segment body are fixedly provided with metal connectors, the outer sides of the metal connectors are provided with grooves for containing water stops, and the water stops are installed inside the grooves; and an outer protecting layer is arranged on the outer side of the segment body, and the outer protecting layer is a polyurea layer combined on the outer side surface of the segment body. The connecting structure is composed of two adjacently arranged shield tunnel segment structures and a connecting part for connecting the two shield tunnel segment structures. A connecting steel plate is composed of a middle arc-shaped section and flat sections on two sides. The shield tunnel segment structure and the connecting structure thereof have the characteristics that thickness is small, strength is high and the connectors are not prone to damage; and the connector deformation control effect is good, the seam waterproof effect is good, durability is high, and repairing is convenient.