An experimental investigation of water droplets impinging with a liquid film of water flowing on a 20°-tilted aluminium board was carried out. The effects of impinging droplet size, velocity and liquid film parameters on splashing were both qualitatively and quantitatively studied and discussed. The evolution of a non-symmetric crown was characterized by investigating the normalized crown height and a non-symmetry factor versus the normalized time, and the breakup of secondary droplets was found influential to the crown evolution. An increase of film velocity and depth reduced the crown height, but it does not affect the non-symmetry factor until the crown started to collapse. Threshold of splashing was investigated, and it was found that the threshold can be well described by the model reported in Ref. [4].