Abstract: The offshore oil platform whose design life is about to expire can be extended service through overall upgrading and modificating, and the structural modification about accommodation is an important part. Through the overall modeling of Suizhong 36-1A offshore platform accommodation, expounds how to design the epitaxial structure to create new rooms to expand the living area, points out the key points of modeling used by SACS software, and analyzes how to set up the load of operating condition and extreme condition, at last, calculates the strength of the modificated accommodation. The calculation result proves the correctness and feasibility of this accommodation modificating method, which is of reference for similar projects in the future.