The invention relates to an automatic fire extinguishing method for a suspended type storage tank, and mainly solves the problems that in the prior art, a fire extinguishing system is slow in response and extra power is needed. The automatic fire extinguishing method well solves the problems by adopting the technical scheme that an extinguishant carrier 2 is arranged above a storage tank, the extinguishant carrier 2 is filled with an extinguishant 3, and the extinguishant carrier 2 is made from a material which is easy to melt in fire; when a fire happens to the storage tank, the extinguishant carrier 2 is molten, and then the extinguishant 3 falls to a fire point to extinguish the fire in time under the action of gravity. The method can be applied to fire extinguishment of the storage tank.