Abstract: Based on stratified swirl flame, the lean blowout characteristics of three swirl intensities, three air split ratios and four pilot stage equivalence ratios were studied by experimental and numerical methods. The blowout boundary can be obtained by gradually reducing the main stage fuel flow until blowout occurs with fixed pilot stage equivalence ratio. The results show that, the flame root can keep a stable state in a wide range when the pilot stage equivalence ratio is high. Therefore, the blowout boundary of the stratified flame in this case is wide. Blowout mainly includes several main processes such as flame lengthening, corner vortex flashback, and flame axial movement. The numerical method can capture the main characteristic phenomena of the blowout. The three prediction methods of blowout boundary are discussed. The feature temperature method is selected to determine the new blowout boundary judgment standard, and the prediction method of blowout boundary applicable to this study is obtained.