The present invention discloses a trichlorosilan device for preparing silane and method therefor. The characteristics comprise a lower cylinder, a middle cylinder and a upper cylinder which lay in bottom-up order followed by decreasing diameter and spaced apart from each other. On the top of the lower cylinder provided are a lower top liquid inlet and a lower top gas outlet. The lower top liquid inlet extends to the center of the lower cylinder and connects to a feed sparger. A lower catalyst layer is provided below the feed sparger. Two packing layers are provided below the lower catalyst layer. On the top of the middle cylinder provided are a middle top liquid inlet and a middle top gas outlet. Below the middle top liquid inlet provided is middle liquid distributor. A middle catalyst layer is provided below the middle liquid distributor. On the top of the upper cylinder provided is a upper top liquid inlet. Advantages are simple in process and less use of auxiliary equipment, comprising two silane reactors and two distillation columns.