Corn Husk contains cellulose which has potential to become a biosorbent of anionic surfactant. This research aimed to know the optimum mass of corn husk biosorbent to reduce the amount of anionic surfactant in detergent waste and knew the characteristic of the biosorbent pores by using Scanning Electron Microscope (SEM). This research used activation method by using NaOH 5 % for 90 minutes, and used mass variation 28 gr, 32 gr, 36 gr. The amount of anionic surfactant was determined with MBAS method. The result of SEM showed that the diameter of the biosorbent pores got larger after being activated from 2.12 nm to 3.41 nm. This experiment showed that activation had removed lignin which was bound to cellulose. The optimum mass of biosorbent was 32 gr which had reduced the amount of anionic surfactant from 92.8 mg/l to 77.9 mg/l with maximum adsorption capacity 0.1862 mg/g.