A process for preparing water glass and activated carbon as by-product from ashed rice husk char includes such steps as burning rice husk to obtain ashed char, mixing it with caustic soda in ratio of10 : 3 in high-pressure reactor, additing water to soak the char, sealing, introducing steam to pressurize, boiling until it reaches 20 deg. Baume, filter, collecting filtrate, boiling dregs, filter to obtain filtrate, merging the filtrates, concentrating to obtain water glass, boiling dregs three times, filter to obtain carbon, wash with hydrochloric acid, filter to obtain carbon, baking, and crushing to obtain activated carbon. Its advantages are simple process and low cost.