Non-contact ballistocardiography (BCG) is used to measure heart rate (HR) by measuring the periodic pressure of blood on the walls of blood vessels during circulation. This pressure causes the periodic weak mechanical movement of various parts of the body, including the head, which is very weak, and the BCG signal extracted from the body movement has a low signal-to-noise ratio, which limits the measurement accuracy of the heart rate. An optical lever is used to amplify the head motion, and a non-contact high precision heart rate detection algorithm named optical lever amplified BCG algorithm (OLA-BCG) is proposed. In the proposed method, a laser is used as the active light source. A plane mirror attached to the head is used to amplify the head motion. At the same time, the weighted centroid tracking algorithm is used to extract the motion trajectory of the head, and the interference noise is filtered out by independent component analysis to obtain BCG signal. Finally, the extracted BCG signal is analyzed and the heart rate is calculated. Experimental results show that the proposed OLA-BCG can effectively improve the signal-to-noise ratio and measurement accuracy.