An experimental study is presented to clarify impact behaviors of high-speed fine droplet onto horizontal dry surfaces by using our original system,which can provide high-speed fine droplet with average impact velocity of approximately 150 m/s and average diameter of approximately 50μm,which are similar to those of spray impingement on pistons inside automotive diesel engines.The impact behaviors of the high-speed micro-droplets for the case of water and light oil,which can be obtained in this investigation,are quite different from the splash mode behavior predicted by using previous classifications.In general,diameter of impacted droplet probably increases with the elapsed time up to the maximum diameter,which might be probably related to the droplet diameter before impact.The diameter,in turn,decreases,and finally the diameter reaches the contraction diameter when the high-speed fine droplets of water are impacted onto each three surfaces employed.For the case of high-speed fine droplet of water,the stick mode behavior and the “divided” mode behavior can be observed.It is remarkably suggested that the divided mode behavior differs significantly from conventional modes.For water droplet,the stick mode behavior and the divided mode behavior can be sequentially observed as the maximum diameter increases.On the other hand for glycerine droplet,the stick mode behavior and the spread mode behavior can be sequentially apparent when the maximum diameter increases.The contraction diameter depend on the maximum diameter.In particular for water droplet,the contraction diameter is significantly affected by the impact modes.It seems that the surface roughness may influence the diameter ranges of the impact modes for the high-speed fine droplets of water and glycerine.The spread mode of impact behavior can be apparent for the high-speed fine droplets of light oil which hardly exhibits the shrink motion.