Abstract: In order to evaluate the possibility of extracting astaxanthin from Phaffia rhodozyma disrupting cell wall by acid method, influences of several cell-wall disrupting factors such as type of acid, concentration of acid, disrupting time and liquid to solid ratio on extracting astaxanthin from Phaffia rhodozyma were studied and conditions used to disrupt the yeast cell wall were optimized. Lactose acid was the best considering the ability of disrupting the yeast cell wall and relatively week ability of discomposing astaxanthin. Concentration of lactose acid and temperature used to treat the cell had significant effects on extraction ratio of astaxanthin. On the contrary and the ratio between acid solution and yeast cell, and time used to treat the yeast with acid appeared to have no significant effects. The optimal conditions gained by orthogonal experiment were: concentration of lactose acid 6 mol/L, temperature 30℃, time 5 min, ratio between acid solution and yeast 15 mL/g. Under the optimal conditions, the extraction ratios of astaxanthin and total carotenoid were 1374.7 μg/g and 1707.9 μg/g, respectively, and 80.4% of total carotenoid was astaxanthin. The optimal condition was easy to be put into use, would not lead to any residual poison, could get high extraction ratio and high quality astaxanthin, so it was prosperous to be put into industrial use.