The microwave pyrolysis of cotton stalk was investigated to determine the effects of three different catalysts on the yields of product and the components of bio-oil. Research results showed that NaOH, Na_2CO_3 and H_3PO_4 can all decrease the yield of liquid and increase the yields of solid and gas, the liquid yield decreased to 23.8%, 22.1% and 26.7% from 28.9% without catalysts, respectively. The main components of bio-oil from microwave-assisted pyrolysis of cotton stalk without catalysts are acetol, fu...