The invention discloses a large-capacity armored undersea optical fiber cable quick connecting joint box and a connecting method thereof. The joint box comprises a supporting seat, a sealing seat, an armored terminal locking and fixing device, an electric appliance connector, an optical fiber storage disc, a sealed cylinder and a bending limiter. The upper surface and the lower surface of the supporting seat are fixedly connected with the optical fiber storage disc. Two ends of the supporting seat are connected with the sealing seat. The armored terminal locking and fixing device is connected with the sealing seat. Two ends of the electric appliance connector are fixedly connected with a metal conductor in the undersea optical fiber cable. The sealed cylinder sleeves the supporting seat, the sealing seat and the armored terminal locking and fixing device. The bending limiter is connected with nuts at two ends of the sealed cylinder. The large-capacity armored undersea optical fiber cable quick connecting joint box and the connecting method thereof have advantages of simplifying structure design, improving fiber storage capacity, realizing functions of electric connection and different-cable-type transition connection, reducing number of laid undersea cables and reducing construction cost in laying. Furthermore the large-capacity armored undersea optical fiber cable quick connecting joint box and the connecting method thereof have advantages of easy operation, effective machining cost reduction, effective on-sea construction cost reduction and wide market prospect.