The shipping economy is developing with the continuous expansion of the world trade. The number of merchant ships has been increasing, especially the demand for bulk cargoes, such as oil and ore, has increased sharply. Ships tend to be large-scale. The emergence of ultra-large oil tankers and ultra-large ore ships not only facilitates the maritime transportation, but also increases the risk of maritime transportation. Once an accident occurs, it will cause huge economic losses and immeasurable marine environment pollution. The ship turning is introduced based on the Nomoto mathematical model. The MATLAB simulation of the ship turning test under the certain marine environment interference has been carried out for the teaching practice ship Yukun of Dalian Maritime University, and the simulation curve has been analyzed. At the same time, the speed drop during the ship turning is studied. By taking the speed drop estimation formula that was proposed by Li Zongbo as an example, a 300 000 tonnage oil tanker has been examined to simulate the experimental results of Li Zongbo and others with MATLAB based on the Nomoto mathematical model. The applicability of the speed drop estimation formula to large ships is verified by comparing the simulated results with the actual speed in the turning motion. Finally, it is summarized to present some shortcomings in the current study.