This chapter introduces a robust human face tracking scheme for vision-based human-robot interaction, where the detected face-like regions in the video sequence are tracked using unscented Kalman filter (UKF), and face occlusion are tackled by using an online appearance-based scheme using principle component analysis (PCA). The experiment is carried out with the standard test video, which validates that the proposed PCA-based face tracking can attain robust performance in tackling face occlusions.