Abstract: Life cycle inventory(LCI) can be used to quantify the energy input,material assumption and environmental emission of a product system in their whole life cycle,and identify measures to improve their environmental property.A data flow balancing algorithm was built by the definitude of LCI steps and the flow sheet modeling,and LCI data compiling method was also gained based on the recursion algorithm for the unit process data flow.Furthermore,the built LCI algorithm was used to verify and practise life cycle inventory of iron and steel production．