A water-proof junction box and a water-proof connector assembly therein are provided. The water-proof junction box includes a junction box body, a junction box cover and at least one water-proof connector assembly deposited at a lateral of the junction box body. The water-proof connector assembly includes a tube, a water-blocking sleeve, a pressing element and a fastening element, all of a cannular shape. Therein, the tube and the junction box body are integrated, and the tube has an externally threaded portion. The water-blocking sleeve is for being inserted into the tube and has a flange as well as a sleeve portion. The pressing element is for being mounted around the sleeve portion of the water-blocking sleeve. The fastening element is internally formed with an internally threaded portion for screwingly coupling the externally threaded portion of the tube.