This study aims to identify key operating variables affecting N2O emission from oil shale-fired circulating fluidized bed (CFB). These operating variables include bed temperature, excess air factor, particle size, secondary air ratio, Ca/S ratio, circulation rate and bed material height. Using an oil shale-fired CFB pilot setup composed of a quartz tube and heated by all electric heater, the experiments of N2O emission were carried out with oil shale test samples obtained from Huadian, China. Grey relational method was used to treat the experimental data. Calculation results indicate that bed temperature is a variable most closely related to changes in N2O emission; the effects of secondary air ratio and circulation rate are negligible. The operating variables sequenced in order of decreasing effect are bed temperature, excess air factor, Ca/S ratio, particle size, bed material height, secondary air ratio, circulation rate. The experimental results and grey relational analysis call provide reference data for design of oil shale-fired CFB furnaces.