Liquid metal， as a highly efficient heat transport medium， is very important in the design of magnetic confinement fusion devices. Predicting the solidification law of liquid metal under strong magnetic fields is an important issue. This article uses a high-speed camera to capture the phenomenon of gallium indium tin alloy impacting metal solid walls and solidifying under the action of a vertical magnetic field. Using image processing technology， it summarizes the characteristics of metal droplet impact spreading， rebound， and solidification under different undercooling temperatures， impact velocities， and magnetic induction intensity ranges of the bottom plate. The bottom plate temperature is 20， -30， -40， and -50 ℃， the impact velocity is 0.45-1.71 m/s， and the magnetic field strength range is 0-1.2 T. Experimental phenomena show that when droplets impact isothermal walls and supercooled walls， the dimensionless scaling rate of the maximum spreading factor follows the classical theoretical prediction relationship. The magnetic field initially promotes and then suppresses the rebound height of droplets. The empirical relationship between the maximum spreading factor and N under the action of magnetic field is derived. The magnetic field inhibits the separation of droplets when they hit the supercooled wall， and weakens the oscillation in the height direction to promote solidification.