The invention discloses an insulation detection method of an electric vehicle power battery pack. According to a voltage sampling signal of the battery pack and a voltage sampling signal of a sampling measuring resistor, the insulation resistance value of high-voltage positive and negative buses on a vehicle body is accurately calculated, under the condition that insulation is lowered or damaged, the fault position is accurately judged, and therefore which battery in the series connection battery pack is abnormal in insulation of positive and negative electrode columns is determined. The insulation detection method of the electric vehicle power battery pack is applicable to a power battery box of an electric vehicle and used for judgment when slight insulation fault of positive and negative electrodes of batteries of the power battery box or connecting wires occurs to the vehicle body, and the situation a huge short circuit current caused by the battery insulation fault further causes a fire, equipment damage and personnel injuries is prevented. The detection method solves the safety problem of the single-point insulation used by the power battery box and has great importance and effects on industrial development of electric vehicles.