Abstract: There is a lot of waste heat being generated during the production of liquid NaCN by light oil cracking process.Part of heat is used for preheating the raw materials and the remaining heat is taken out of system through recycling cooling water and discharged to the atmosphere by the cold water columns.Therefore，a lot of heat energy is wasted.A reusing method of waste heat in the industrial chemical production was introduced.The generated waste heat could be brought into heating system of factory to replace steam after the reconstruction of technology，equipment，and pipeline in the NaCN workshop.Thus the waste cracking heat could be reused.After calculation of waste heat energy efficiency，a lot of waste heat could be recycled annually. The reconstruction could not only save the coal consumption，but also could reduce environment pollution.

Key words: light oil cracking, sodium cyanide, waste heat reusing