Abstract: In order to analyze and discuss misfire causes of the detonator in the underground mine blasting operation, with the establishment of the similar model 0 f the cross section detonator lasting net line in the underground mine roadway, the water bearing rate and the electric conductivity performance tests of coal were indivi dually conducted. The underground series blasting net line grounding test and the detonator foot line connection mode influence test showed that the higher of the coal water content rate, the lower the electric resistance value would be.The grounding electric current occurred at the grounding location in the blasting net line would redu ce the electric current in the completed net line. The different connection mode of the detonator foot line would directly increase the total electric resistance of the compl eted net line.All above conditions would reduce the total electric current of the completed blasting network which would cause a misfire by the insufficient firing current of the detonator.