A driving circuit and a gray insertion method of a liquid crystal display (LCD) are provided. The gray insertion method includes analyzing whether a current frame belongs to a dynamic frame or a static frame. When the current frame belongs to a dynamic frame, charging time of a gray insertion image is extended. When the current frame belongs to a static frame, the charging time of a gray insertion image is shortened. As a result, motion blur on the LCD can be reduced and image quality can be increased.