The invention relates to a diagnosis method and an apparatus of beam tube blocking of a mining fire monitoring system. The method includes: the flow of a beam tube is detected in real time; the flow of the beam tube detected in real time and a flow standard value are compared, and if the difference is greater than a set threshold, it is determined that the beam tube is blocked. According to the method, the occurrence of blocking can be determined in real time via the monitoring of the flow of the beam tube, and hidden risks are eliminated.