The invention belongs to the field of dynamic behavior monitoring of a laser welding puddle and a key hole, and discloses a method for monitoring dynamic behavior characteristics inside the laser welding puddle and the key hole. The method comprises the following steps: 1, a point light source, a high-temperature-resistant transparent glass, a high-speed camera and a computer are provided, wherein the high-speed camera is electrically connected with the computer; 2, a metal plate to be welded is arranged on a welding support platform, and the high-temperature-resistant transparent glass is arranged on the side, adjacent to the high-speed camera, of the metal plate; and 3, the point light source illuminates the high-temperature-resistant transparent glass and the metal plate, the high-speed camera shoots the side face of the metal plate adjacent to the high-temperature-resistant transparent glass through the high-temperature-resistant transparent glass in real time and transmits the shot images to the computer in real time, and the computer is used for processing and displaying the received images in real time. The method for monitoring the dynamic behavior characteristics inside the laser welding puddle and the key hole is feasible, simple and reliable, and the dynamic behavior characteristics inside the welding puddle and the key hole can be monitored visually in real time.