The invention relates to a method for preparing lanthana (
cerium oxide) with a low content of iron and high specific surface, which is characterized by comprising method of removing Fe from 
lanthanum and cerous 
rare earth carbonate and the method of controlling the specific surface of the lanthana (
cerium oxide); the method for removing Fe adopts single-stage extraction or serial extraction with a complexation 
settling method, namely firstly, removing Fe in LaCeCL6 to be less than 0.005wt% by using an extracting agent with an extraction method and reducing the content of Fe in LaCeCL6to be less than 0.002wt% by using a complexing agent, wherein the extracting agent is C8-C10 
tertiary amine and the complexing agent is sulpho-amino niobate; 
lanthanum carbonate or cerous 
carbonate is precipitated from the 
ammonium hydrogen carbonate or the 
sodium carbonate from which Fe is removed; the specific surface of the 
lanthanum carbonate or the cerous carbonate is controlled by the method of increasing the temperature in a gradient elevation way, the temperature is increased to be below 800 DEG C from 320 DEG C in a gradient elevation way and is reduced to the 
room temperature. The method has the advantages that the lanthana (
cerium oxide) with a low content of iron and high specific surface, which is produced by the technique method fully satisfying the requirement on the 
raw material required by the accurate and high-speed 
rare earth polishing material, has stable quality, is easy to implement the industrial production, and can reach the following specific technical indexes with TREO being more than or equal to 90 percent, La2O3 / TREO being 25 percent to 30 percent, CeO2 / TREO being between 70 percent and 75 percent, Pr6O11 / TREO being less than 0.002 percent, Fe2O3 being less than 0.002 percent, and the aged specific surface being more than 30m / g.