Based on the dangers of suspended oil mist microparticles from machining to the environment and health of worker. A theoretical analysis on the generation mechanism of cutting fluid oil mist and an experimental study on its influencing factors were carried out in this paper. The experiment was conducted in closed lathe with flood cutting fluid feed system. A droplet diameter measuring system was equipped in the dense region of oil mist, which enables to observe the droplet distribution in air and scan the morphology of a single droplet accurately through its confocal microscopy. Droplet distribution and diameter were calculated through computer. In the experiment, effects of influencing factors on the oil mist concentration and average droplet diameter were discussed by controlling the revolutions per minute (rpm) of the main axis and cutting fluid flow, respectively. Experimental results demonstrated a significant effect of rpm on the characteristics of cutting fluid oil mist. As the rpm increased, the average droplet diameter decreased, whereas the oil mist concentration increased. As the cutting fluid flow increased, both of average droplet diameter and oil mist concentration increased.