In order to upgrade the flexibility and expansibility of iWSN sensing module, the iWSN expansion module is developed to connect to the iWSN sensing module. By means of iWSN expansion modules, the iWSN sensing module can offer more current and temperature measurement channels. The iWSN expansion module is energized by iWSN sensing module so that there is no external power supply needed. For convenient setting up and maintaining the application, the iWSN expansion module provide removable screwed terminal block, wall-mount mechanism and magnet adsorption for installation, and also allows connecting different measurement range of CTs to fit various applications. More kinds of IO interface will be designed to rich the iWSN functionalities and unleash the power of iWSN sensing modules.