Abstract: Experiments that use single-pulse laser to ablate small steel ball in atmosphere were conducted. In these experiments, the propulsion efficiency parameters were obtained and different phenomena for the steel ball in front and back of the focus were analyzed in detail. To get a series of experiment data, experiments for different mbient conditions and different target materials were conducted and the propulsion parameters were obtained, and the experiment data were compared with those of overseas and numerical results.Experimental results showed that the material of target and the laser intensity were the main factors influenced the mechanical coupling coefficient(cm), and the cm value increased a few with the decreased of ambient pressure.