In the framework of this paper, the authors present briefly the methodology of assessing the strength safety for support steel structure of fixed offshore platform subjected to random wave loads in deep water, and its application to conditions of Vietnam sea in from 200m to100m water depth. The paper content is taken from the reseach results of authors in the National Research Project KC.09.15/06-10, performed mainly by lnstitute ICOFFSHORE-NUCE.