The invention discloses a defrosting and demisting air outlet blade angle regulating system, which comprises an air outlet device, a blade angle regulating device, a position sensor and a controller, wherein the air outlet device comprises an air outlet framework and blades movably arranged in the air outlet frame, the position sensor is used for detecting the position information of a driver seat and transmits the position information to the controller, the controller receives the position information from the position sensor, judges the human body percentile of a driver on the driver seat according to the position information and determines the blade angle on the basis of the human body percentile, and the blade angle regulating device regulates the blade angle under the control of the controller. The blade angle regulating device is integrated on a defrosting and demisting body arranged on a door internal decoration plate in the prior art, and the structure is simple. The defrosting and demisting air outlet blade angle regulating system has the advantages that the human body percentile of the driver is judged according to the position information of the driver seat seated by the driver, the blade angle is automatically controlled and regulated, and the active safety is improved.