The present invention discloses a humidity preception device of microwaven oven with a ventilation cover. Said invention includes: upper cavity of heating chamber, exhaust motor component placed in the rear portion of upper cavity of heating chamber, exhaust hole palced near by exhaust motor component and communicated with the heating chamber, air inlet placed in the front of upper cavity of heating chamber and communicated with heating chamber and humidity sensor placed near by exhaust hole and used for determining humidity of exhausted air. In the described upper cavity of heating chamber an air channel for guiding air flow is set, and the humidity sensor Sb is placed on the air channel correspondent to upper portion of exhaust hole. |