Rice straw is one of the main renewable energy sources in Korea, and bio-oil from rice straw is produced using a bench-scale plant that is equipped mainly with a fluidized bed and a char removal system. We investigated how the reaction temperature affected the production of bio-oil and the efficiency of a char removal system. To elucidate how the temperature was dependent on the production of bio-oil, experiments were conducted between 400 degrees C and 600 degrees C at a feed rate of similar to 1 kg/h. The mass balance was established in each experiment, and the produced gas and oil were analyzed with the aid of gas chromatography and a gas chromatography-mass spectroscopy (GC-MS) system. The effect of pretreating rice straw was also investigated by comparing the yield of bio-oil and the content of alkali metals in the bio-oil from the experiments on unwashed rice straw with the corresponding values of washed rice straw. The char removal system is composed of a cyclone and a hot filter. After every experiment, we examined the particle distribution of each char and the content of solids in the bio-oil, to demonstrate the efficiency of the char removal system. In the experiments, we observed that the char removal system and the pretreatment effectively reduced the content of alkali metals in the bio-oil, and that the optimum reaction temperature range for the production of bio-oil is 410-510 degrees C.