The invention relates to the technical field of nitric oxide sensors, and discloses a diesel engine nitric oxide detection volume treatment method and system, accordingly, accurate calibration of thenitric oxide sensors is achieved, and accurate measurement on the nitric oxide emission is achieved. The method comprises the steps that the work state and parameters of an engine are obtained, and the parameters include the rotation speed and the torque; when the work state is the motored state, zero point deflection calibration treatment is conducted on the nitric oxide detection volume; and when the rotation speed and the torque continue for the preset time within the set range and it is monitored that a selective catalytic reduction SCR postprocessing systems does not spray urea, compensation calibration treatment is conducted on the nitric oxide detection volume. The embodiment is applied to the treatment process for the nitric oxide detection volume of the nitric oxide sensors.