This paper mainly introduces the causes and treatment methods of boil off gas (BOG) during the low temperature storage and transportation of liquefied ethane, and proposes a process optimization scheme to solve the problems of high energy consumption of BOG re-liquefaction process and high percentage of gas phase in the fluid returned to storage tank after liquefaction. HYSYS simulation software is used to simulate and analyze the process flow of liquefied ethane BOG re-liquefaction before and after optimization. The results show that the optimized re-liquefaction process can improve the energy efficiency by 10% and reduce the percentage of gas phase in the fluid returned to storage tank after liquefaction by 50%.