Highly porous activated carbon fiber with excellent surface area has been prepared using silk cotton fiber as a precursor. The Activated Silk Cotton Fiber (ASC) has well developed porosity with rose flower like structure. The BET surface area of the prepared adsorbent is 1041.08 m(2)/g with a total pore volunof 0.4944 cm(3)/g. The adsorption capability of the prepared adsorbent ASC has been analyzed using methylene blue (MB) dye. The effect of pH indicates that ASC has its maximum adsorption at a pH of 10. On analyzing the kineties,of MB adsorption, the pseudo-second order kinetic model describes the adsorption with good r(2) value of 0.9895 < r(2) < 0:9997. The maximum Langmuir monolayer adsorption capacity is found to be 80.65 mg/g at 45 degrees C. The experimental results and the thermodynamic studies prove the physisorption nature of MB adsorption onto ASC.