The invention discloses an alarm temperature threshold value judging and alarming method based on a passive wireless temperature measuring device. The method includes the steps of determining an alarmtemperature threshold value of the passive wireless temperature measuring device by taking the current environment temperature into consideration according to the historical collected temperature data of the passive wireless temperature measuring device and historical meteorological data of the place where the device is located, and conducting alarm prompt based on the temperature information data acquired by the current passive wireless temperature measuring device to achieve the purpose of rapidly finding out abnormal points and eliminating the potential risk. The method overcomes the defects that an alarm temperature threshold value of the passive wireless temperature measuring device is set by experience, is fixed and inaccurate, and that a common active temperature measuring device cannot work and cannot be replaced timely after power failure. The reliability of analyzing data sources is improved.