Abstract: To obtain crab shell powder with smaller average particle size,and more evenly distribution,pretreatment was carried out with lactic acid to shorten the time and ultrafine grinding was used to reduce the particle size.The single- factor experiment and response surface method( RSM) were employed to optimize the technological conditions,including the soaking liquid concentration,ratio of material to solvent and softening time. The optimal conditions were set as lactic acid concentration of 0.663%,soaking time of 15.5 min,and liquid- solid ratio of 14∶ 1.Under the set conditions,the particle size D10、D50、D90of crab shell powder was respectively 1.31、3.874、6.798 μm,specific surface area was 850.1 m2/ kg. Compared with crab shell coarse powder from market and controlled superfine powder,the average particle D50 reduced 26.75 and 2.10 times,the specific surface area increased 11.12 and 0.97 times.At the same time,the crab shell powder grinding degree was enhanced and provided a theoretical basis for the intensive processing of crab shell.