The invention discloses passive self-breeding high-heat pasty fluid for automatic stainless steel welding. The passive self-breeding high-heat pasty fluid comprises a basic recipe composition and a binding agent. The weight ratio of the binding agent to the basic recipe composition is 29:100. The invention further provides preparation and using methods of the passive self-breeding high-heat pasty fluid for automatic stainless steel welding. The pasty fluid for welding adopts boron powder and other new reducing agents as combustion components, heat energy released by a reagent which has the high exothermicity after being ignited is sufficient to enable combustion products such as copper, iron, nickel and fusion welding materials to be metallurgically combined with welded parent metal through wetting, diffusion, reactive crystallization and other mechanisms, and therefore automatic welding is completed; welding work of metal like carbon steel is efficiently, easily and conveniently completed under the situation that no external power sources or gas sources or other energy sources or no other devices or tools are used on the condition of any special places and weathers.