The invention provides an electrochemical method for directly preparing silicon nano power and nanowires (tubes) from a compound SiX or a mixture containing the compound SiX, which is characterized by comprising the following steps of: by using the compound SiX or the mixture containing the compound SiX as a cathode, setting an anode; placing the anode in electrolyte containing metallic compound fused salt; applying voltage between the cathode and the anode; controlling reaction conditions; and preparing the silicon nano power and the nanowires (tubes) on the cathode. The invention has the advantages of short production process without pollution, easy operation and material obtaining, inexpensive equipment and easy continuous production, also opens a new field for applying the electrochemical method to the preparation of one-dimensional nano materials and explores a new way for preparing the silicon nano power and the nanowires (tubes).