A portable wireless alarm system includes at least two alarm devices each of which includes a signal generator for generating an action signal, wherein the alarm devices are communicatively networked with each other by means of radio frequency to contribute a security network in such a manner that, within the security network, when one of the alarm devices is triggered to generate the action signal, another alarm device is automatically triggered by the action signal to produce alert signal, so as to enlarge a coverage area of the alarm device. In addition, the alarm device is a portable wireless alarm device that is communicated with an alarm activator by means of radio frequency signal to remotely control the alarm device to be activated. Therefore, the portable wireless alarm device is capable of wirelessly setting up at a designated location with free installation to ensure the best security.