A method for driving virtual facial expressions by automatically detecting facial expressions of a face image is applied to a digital image capturing device. The method includes the steps of detecting a face image captured by the image capturing device and images of a plurality of facial features with different facial expressions to obtain a key point position of each facial feature on the face image; mapping the key point positions to a virtual face as the key point positions of corresponding facial features on the virtual face; dynamically tracking the key point of each facial feature on the face image; estimating the key point positions of each facial feature of the current face image according to the key point positions of each facial feature on a previous face image; and correcting the key point positions of the corresponding facial features on the virtual face.