The combustion of cylinder lubricating oil is one of the major resources of PM emissions of low-speed 2-stroke marine engines. For pre-mixed gas engines, the auto-ignition of cylinder oil might result in knock or more hazard abnormal combustion — pre-ignition. The evaporation is a key process of the auto-ignition of cylinder oil droplets. The evaporation behavior has a profound impact on the auto-ignition and combustion processes of cylinder oil droplets. This paper applied a suspending apparatus to investigate the evaporation characteristics of cylinder oil droplets and base oil droplets. The effects of environment temperature and droplet diameter on the evaporation process were measured and analyzed. The results indicate that the evaporation of cylinder oil includes heating, evaporation, pyrolysis, and polymerization. Under high temperature conditions, the pyrolysis process caused the explosion of the oil droplets, and the evaporation curve appeared intensive waving. The major composition — 150 BS base oil droplets also appeared such phenomenon. But another major composition— 400 SN base oil did not show such characteristics. The lifetimes of cylinder oil droplets tightly correlate with ambient temperature and droplet diameter. Under high temperature condition, the lifetimes of cylinder oil droplets rapidly decrease when the ambient temperature is increased; under the same ambient temperature condition, the lifetimes of cylinder oil droplets rapidly decrease when droplet sizes are decreased.