By using multi-beam optical interferometry,the spreading flow phenomenon of a micro-oil droplet closed to a static ball-on-disc contact region was observed experimentally in order to study the lubrication mechanism of microoil droplets.The results show that the micro-oil droplet spreading around the ball-on-disc contact rim is due to capillary force.The spreading velocity is increased with the increasing of micro-oil droplet volume,whereas decreased with the increasing of oil viscosity.Moreover,the spreading velocity of micro-oil droplets is quite large on the high energy contact surface.When the surface tension of lubrication oil is quite small,the primary radius of oil droplets spreading is getting bigger,the distance of spreading is obviously reduced,and the phenomenon of second time of spreading is produced.