The application discloses a new energy vehicle and an insulation detection method and a system thereof. The method comprises the following steps: inputting an original injection pulse to a new energy vehicle, and collecting a pulse signal currently output by the new energy vehicle to get a real-time recovery pulse; judging whether the voltage amplitude of the real-time recovery pulse is beyond a measurable range, and if the voltage amplitude of the real-time recovery pulse is beyond the measurable range, adjusting the voltage correspondingly to enable the voltage amplitude of the real-time recovery pulse fall into the measurable range; and judging whether the influence of the current voltage of a Y capacitor on the real-time recovery pulse can be neglected, and if the influence of the current voltage of the Y capacitor on the real-time recovery pulse can be neglected, determining a shortest pulse signal time for completing insulation detection, taking the time as the pulse time period of the current injection pulse, inputting an injection pulse corresponding to the pulse time period to the pulse input end, collecting a recovery pulse corresponding to the injection pulse, and calculating the value of insulation resistance according to the injection pulse and the recovery pulse. The insulation detection speed of new energy vehicles can be improved.