The invention discloses a method for adding lime in the dissolution process of diaspore and relates to a production technology for aluminum oxide, in particular to an improvement on a method for adding lime in the dissolution process for producing aluminum oxide with diaspore as the raw material. The method is characterized in that lime milk needing to be added in the dissolution process of diaspore is filtered and drained through a plate-and-frame filter, a filter cake obtained after draining is added into an ore pulp tank to be mixed with ore pulp, and then the dissolution process is performed. According to the method for adding lime in the dissolution process of diaspore, lime milk moisture is independently removed through the plate-and-frame filter press, and a large amount of moisture can be removed without mixing ore pulp and then performing filtering, so that system dilution is greatly reduced, cost is reduced, and production efficiency is improved.