Abstract: Because of bad contact or mechanical damage,the coal power supply system might produce series arc fault. Series arc fault is one of the causes of electrical fire in coal mines. There may be inflammable and explosive materials such as gas and coal dust in the underground. It is not suitable to carry out series arc fault experiment,and thus a lot of fault diagnosis samples cannot be obtained,which brings difficulties for arc fault diagnosis. In order to study the typ- ical characteristics and diagnostic methods of series fault arcs in mine power supply system,a series arc fault simula- tion model based on the Mayr-Schwarz arc mathematical model was established for mine power supply system and the performance of this simulation model was evaluated in this paper. Then it simulated and analyzed the electrical faults such as series arc fault,over voltage,single phase ground,two phase ground short circuit,two phase short circuit,three phase short circuit in the coal mining system,belt conveyor system,pump house drainage system,lighting system of mine power supply system. Also,the series arc fault characteristic parameter database of mine power supply system was established by using Zero-crossing point,peak-to-peak value,variance,kurtosis coefficient,margin factor,harmonic dis- tortion rate,unilateral power spectrum frequency variance,wavelet packet coefficient energy entropy,wavelet packet coefficient peak-to-peak value as feature variables. Finally,the paper comprehensively compared the performance of decision tree,K-nearest neighbor and Bagged trees multi-classification pattern recognition method in fault arc diagno- sis,phase selection and anti-load current fluctuation disturbance,anti-background noise disturbance,and proposed se- ries arc fault diagnosis method for K nearest neighbor mine power supply system. The results show that the established series arc fault simulation model can be used to simulate and analyze the series arc fault of mine power supply system and the database established in this paper can reflect the typical characteristics of series arc fault in mine power supply system. It also showed that K-nearest series arc fault diagnosis method can be used for the series arc fault diagnosis and phase selection of mine power supply system.