The DNV·GL new rules give the clear requirements for the general design of the open-top multi-purpose vessels. It is necessary to study the changes of the new rules and their influences on the general design of the open-top multi-purpose vessels in order to guide the subsequent research and development design. The changes of the new rules include the most unfavorable spectrum peak period, trim, initial metacentric height and intact stability of the cargo hold after being flooded during the open-top seakeeping model test. The influence of the new rules on the longitudinal strength and the bilge draining system has been analyzed for the 13 000 DWT open-top multi-purpose vessel. The seakeeping model test of the type III open-top multi-purpose vessel is also compared to summarize the measures to reduce green water. The overall longitudinal bending moment and the shear stress of the hull decrease significantly due to the reduced requirement of the water intake height of the cargo hold, which can further save the hull structural steel. The new rules also improve the redundancy of the bilge draining system of the cargo hold, where the redundancy is not only demanded for the bilge pump but also for the bilge piping system with the special emphasis as an annular piping system. The most effective way to reduce the green water is to locate the superstructure at the bow of the ship with the width of the superstructure arriving at the ship breadth, or to install the wave shelter or breakwater with the certain width and height on the bow of the ship to effectively block green water.