The invention relates to an atomizer for petrol-oxygen cutting torch and a torch with the atomizer. The atomizer is comprised of a body of atomizer, preheating oxygen inlet, petrol thin tube, wherein the petrol thin tube is connected with oxygen thin tube so that petrol from the petrol thin tube is broken up and forms very fine droplets by the kinetic energy of the oxygen, and then enters a nozzle of the cutting torch, finally atomized petrol is mixed with oxygen completely and achieves desirable flame. In the torch of the invention, the atomizer is installed in the joint of the cutting nozzle or preheating oxygen tube or self-automatic cutting machine in order to improve operation condition.