The invention discloses a synthetic method and apparatus for trichlorosilane. According to the method, silicon powder with a particle size in a range of 200 to 400 meshes is used for reaction with hydrogen chloride so as to synthesize trichlorosilane; the used silicon powder has a wide particle size range and is low in production cost and reduced in the difficulty coefficient of production; and since the silicon powder in a wide particle size range has low fluidizing gas velocity, the mole fraction of corresponding introduced hydrogen chloride can be reduced during preparation of trichlorosilane, so difficulty of and cost for tail gas recovery is lowered. Compared with silicon powder used in preparation of trichlorosilane in the prior art, the silicon powder in a particle size range of 200 to 400 meshes in the invention has a greater specific surface area, so a gas-solid contact area is increased and reaction intensity is improved; and thus, the production power of the synthetic method and apparatus for trichlorosilane in the invention is improved.