The utility model provides a fiber cable joint box ponding monitoring devices, ponding monitoring devices include that one settles the box -like module in the fiber cable joint box, the system has the top to put the fine movable block of photometry fully in the box -packed module to set up the hole that supplies the optical cable business turn over on the box -like module lateral wall all around of movable block, water expansion's polyacrylic acid class resin material is loaded in the movable block below space in the box -packed module, ponding monitoring method be: A, ) will box -packed module is installed in the fiber cable joint box to connect and install back in the splice box at the optical cable, encapsulate box -packed module in the splice box, B, ) utilizing polyacrylic acid class resin material's high water absorption character, intaking and ponding because of reasons such as the sealing washer are ageing when the splice box, polyacrylic acid class resin material meets water and takes place the inflation in the box -packed module of encapsulation in the splice box, C, ) the maintenance personal passes through OTDR test to the terminal of optical cable section, can accomplish and to whether there being ponding in the circuit intermediate head box making and differentiating.