Method for directly preparing sodium carbonate from underground brine

The invention discloses a method for directly preparing sodium carbonate from underground brine. The method comprises the steps of reacting by using an ammonia process to remove most of magnesium ions in the brine; and then, carrying out secondary refining by using an intermediate material generated in the intermediate process of sodium carbonate production to remove calcium and magnesium ions, wherein the refined brine is used as a raw material for preparing sodium carbonate, and a magnesium hydroxide sediment generated in the process of removing the magnesium ions through reacting by using the ammonia process is used as a magnesium hydroxide product to be sold after being separated and dried. Through comprehensive utilization of resources, saturated brine can be directly used for sodium carbonate production after being refined, the salt yield of the brine is increased by more than 15%, the yield of a salt pan is increased by about more than 50%, meanwhile, components such as calcium and magnesium ions in the brine are also effectively utilized, and the advantage of cyclic economy is sufficiently exerted.