Impingement process of a small droplet on solid wall was investigated with molecular dynamics simulation technique. A liquid droplet consisting of about 14,000 Lennard-Jones particles was thrown with a given speed onto a smooth wall, and the change of its size and shape was analyzed. After the collision, the droplet spreads on a “hydrophilic,” or strongly interacting, wall, but bounces on a “hydrophobic” wall. The spreading behavior is suppressed by surrounding gas.