NOVELTY - Making (M1) controllable crystal form and particle size of the silicon powder, involves dispersing silicon waste into water, adding hydrofluoric acid and hydrochloric acid, regulating solid-liquid weight ratio and stirring, carrying out solid-liquid separation to obtain primary silicon powder, adding hydrochloric acid and nitric acid , soaking, carrying out solid-liquid separation to obtain solid, adding inorganic acid into the obtained solid, stirring and dispersing, performing solid-liquid separation, washing; and crushing the solids to give the product.    USE - In the preparation of controllable crystal form and particle size of the silicon powder which is useful for casting ingot (claimed), and used in producing solar polycrystalline silicon ingot.    ADVANTAGE - The method has high efficiency, and simple technic; and is easy to produce in large scale. The obtained controllable crystal form and particle size of the silicon powder provides controllable granularity for casting ingot when the ingot is not easy to melt; and effectively removes metal impurity.    DETAILED DESCRIPTION - Preparing (M1) controllable crystal form and particle size of the silicon powder, involves (i) stirring and dispersing silicon waste into water, adding hydrofluoric acid and hydrochloric acid, regulating the solid-liquid weight ratio of 1:1-1:20, and stirring for 10-120 minutes, carrying out solid-liquid separation to obtain primary silicon powder, where the total amount of the hydrofluoric acid and hydrochloric acid is 0.1-2 times of the mass of the waste silicon material, (ii) adding hydrochloric acid and nitric acid to the primary silicon powder of step (i), stirring and dispersing for 0.5-2 hours, soaking for 0.5-10 hours, then carrying out solid-liquid separation to obtain solid, where the adding amount of hydrochloric acid and nitric acid dispersed in pure water is 0.1-2 times of the mass of the primary silicon powder; (iii) adding inorganic acid into the obtained solid of step (ii), adjusting solid-liquid weight ratio of 1:1-1:20, stirring and dispersing for 0.5-2 hours, performing solid-liquid separation, washing the obtained solid with pure water for 2-3 times until the pH is neutral, where the amount of inorganic acid is 0.01-0.5 times of the mass of the obtained solid of step (ii); (iv) drying the solids of step (iii) in a vacuum drier at 30-120 degrees C, drying for 2-24 hours to obtain the silicon powder, where the granularity of the silicon powder is 10 mu m to 5 cm; and (v) crushing the solids of step (iv), and then sieving with screen of 30-150 meshes to obtain non-metal material of ingot silicon having particle size of 0.1-0.5 mm, where the part of crushing process with the silicon powder in direct contact is made of nonmetal hard material. An INDEPENDENT CLAIM is included for casting ingot with controllable crystal form and particle size of the silicon powder, where the controllable crystal form and particle size of the silicon powder is made by using the method (M1), where the particle size of controllable crystal form and particle size of the silicon powder is 0.1-0.5 mm.