The invention provides a seal cabin with a water leakage monitoring function, a junction box and a benthonic observing system. The seal cabin with the water leakage monitoring function is characterized by comprising a seal cylinder, end covers which are arranged at two ends of the seal cylinder and a detecting device. Each end cover is provided with a boss structure and fixed on the seal cylinder. A first seal ring is arranged between the end face of the end cover and the seal cylinder. The boss structure is inserted into the seal cylinder. The detecting device comprises a control plate and detecting rings, and each detecting ring comprises an insulation ring and a guide wire ring. The insulation ring is covered on the outer portion of the guide wire ring. The guide wire ring is electrically connected with the control plate. The control plate is arranged in the seal cylinder. Each boss structure is sleeved with the detecting ring. The detecting ring is arranged between the side wall of the boss structure and the inner wall of the seal cylinder. Improvement of reliability of the junction box is achieved.