In this paper, we propose a practical method for eye blink detection using a monocular system. Eye blink detection is an important technology in many situations such as facial action analysis and signal processing. However, automatic eye blink detection is quite difficult since the eye blink is occurred fast. Fast head tracking and eye detection methods are therefore required in real environment. The proposed method is based on the facial feature point tracking algorithm by using particle filtering. The proposed method works at over 60fps and is able to detect accurate blink motion in real time although our system require only one USB camera. In order to confirm the effectiveness, we show some of applications using our blink detection system.