In consideration of the nonlinearity of SO₂ in circulating fluidized bed boiler, a prediction model of SO₂ emissions in flue gas based on support vector machine is proposed. It is complex to directly search the parameters of support vector machine regression, so a method combining single variable search and grid search is applied. The simulation shows that the prediction model of SO₂ emissions in circulating fluidized bed boiler based on support vector machine has good prediction performance.