Aiming at the explosion and fire caused by leakage gas in industrial production, an infrared image leakage gas detection method based on shape and support vector machine(SVM) is proposed. The SVM classifier is trained by using the shape features of the infrared image sample of the leaking gas and the interfering object. The candidate target region is obtained by using the background difference-based motion detection for the infrared image sequence, and then the shape feature is extracted from the candidate target region, and finally the SVM classifier is used to obtain the final detection result. Experiments were carried out using ethylene gas leakage simulation data, and the detection rate was up to 98%. The results show that this method can effectively detect the leakage gas, which greatly reduces the false detection caused by the interference.