Ultrafine needle-shaped wollastonite powder with large aspect ratio has immense application value in industry. There are two ways of increasing aspect ratio of needle-shaped ollastonite powder. One is the good selection of preparation machine with suitable omminution mechenism. The other is the proper processing condition. The authors used a ertical impact-classified mill in the experiment. For the purpose of attaining the preparation im of large aspect ratio, the main technological parameter was adjusted. It is indicated that the mll is quite suitable for the preparation of needle-shaped wollastonite powder, and the adjustment of main parameters (federate, impact rotational speed and classified rotational peed) has a strong influence upon the aspect ratio and the grain diameter of the product.Through the experiment, the authors have succeeded in preparation of needle-shaped wllastonite powder whose average diameter is 3.3μm and whose aspect ratio is 15.