The invention discloses a preparation method of acid-modified superfine shell 
powder. The preparation method is characterized by comprising the following steps: 1) removing the 
cuticle of a shell 
raw material, and then adding water accounting for 20-80% of the weight of the shell subjected to 
cuticle removal, and stirring for 6 to 48 h to prepare 
slurry; 2), adding acid liquor accounting for 5-25% of the weight of the shell subjected to 
cuticle removal in the 
slurry, and stirring to obtain acid-modified shell micro 
powder slurry; 3), carrying out washing, filter pressing, 
drying and 
grinding on the acid-modified shell micro 
powder slurry to obtain modified shell powder with the particle size of 0.5-5 microns; and 4), adding 
purified water in the modified shell powder obtained from the steps 3), mixing into paste, and then adopting a planetary ball milling and 
grinding method to process, dry and crush to obtain the superfine shell powder with the particle size of 0.01-5 microns. The invention further discloses acid-modified superfine shell powder prepared by the method. The preparation method and the product are simple in process, small in equipment investment and low in 
energy consumption. Besides, the prepared modified shell micro powder is good in surface activity.