According to the current design practice of several small-sized offshore mobile units classed CCS, the applicability problems of the rules and regulations about rated person numbers on unit, lifeboat, load line assignment and tonnage measurement, survey access, generator set, boarding and leaving platform facilities, gas detection and alarm system, ballast tank, mooring equipment, submersible pumps, submarine valve boxes, design wind velocity, piecewise spliced legs, container spliced hulls, etc. during the design of small-sized offshore mobile unit are combed systematically, and the corresponding solutions and suggestions are given, which has some guidance to the design of small-sized offshore mobile units in China in the future and provides useful reference for suitable technical requirement research of rules and regulations on small-sized offshore mobile units.