The method has been proposed for the risk assessment of petro-chemical plant, specially which can evaluate relative risk levels on the materials and process-es. The each potential risk of materials and processes are derived numerically and combined these values, finally Fire and Explosion Index was found. Material factor was evaluated with the flammability and the reactivity and process factor with emprical factor called penalty. This F&EI can be performed for relative risk assesment at the whole plant and directely applicable at the line.