1003 readings by PQ（Particle Quantifier）were collected randomly as the sample data,which was generated from the PQ inspecting to the gearboxes oil of 25 CRH1 highspeed electric multiple units.The distribution regular pattern of the CRH1 gearbox PQ data was studied,and the monitoring limited value was calculated by using probability and statistics theory.By applying the PQ monitoring technology to gearbox oil of highspeed electric multiple unit,the primary practice shows that it is feasible to generate the theoretic monitoring threshold value based on a large amount of samples by using parameteric evaluation method of mathematic probability and statistics theory，which provides a condition monitoring reference for the safe operation and condition maintenance of electric multiple unit.