The invention discloses a method for reducing energy consumption in nano calcium carbonate production, and belongs to the field of nano calcium carbonate preparation, the method for reducing the energy consumption in nano calcium carbonate production comprises the following steps: S1, adding water to dilute refined lime milk, adjusting to a suspension with calcium hydroxide concentration of 7-12%, and adding into a carbonization reactor; s2, adjusting the temperature of the calcium hydroxide suspension to 10-40 DEG C, then adding an additive 1 and an additive 2 into the suspension, and uniformly mixing; and S3, introducing carbonization gas with the CO2 volume concentration of 10-100% into the suspension liquid to carry out carbonization reaction, continuously introducing the carbonization gas for 10-30 minutes to carry out over-carbonization when the pH value of the suspension liquid is reduced to 7.0, and obtaining a nano calcium carbonate suspension liquid at the temperature of 30-70 DEG C after the carbonization is finished. According to the method, the productivity and the equipment utilization rate are improved, the production energy consumption is reduced, the produced nano calcium carbonate product is high in activation degree and low in oil absorption value, the process is simple and feasible, existing process equipment does not need to be changed, the production cost is low, and good economic benefits and social benefits are achieved.