The invention discloses a preparation method of triphenylphosphine. The preparation method comprises following steps: (1), a mixed solution prepared from chlorobenzene, toluene and THF (tetrahydrofuran) is pumped into an overhead tank; (2), magnesium chips are fed into a Grignard reaction kettle, a small quantity of the mixed solution is added, a Grignard reaction is triggered, then the remainingmixed solution is dropwise added, and a thermal-insulation reaction is performed; (3), a reaction liquid is pumped into the Grignard reaction kettle, phosphorus trichloride is dropwise added slowly, and the thermal-insulation reaction is performed; (4), centrifugal mother liquor and a scrubbing solution are distilled to recover THF/toluene, toluene is added to residues, materials are transferred into a layering kettle, a diluted hydrochloric acid solution is dropwise added, and a mixed solution is left to stand for layering; (5), an organic layer is washed with water and transferred into a crystallization kettle, a solvent is recovered through distillation, methanol is added to residual materials, and the mixture is heated to be subjected to reflux, cooled to the room temperature and centrifuged; mother liquor is recovered through distillation, methanol is reused, a filter cake is heated in a melting tank and then is subjected to distillation separation, and biphenyl and triphenylphosphine are obtained. The preparation method has the advantages as follows: the technology is reliable and stable, a product is high in yield and purity and has excellent color and luster, reaction timeis short, and the method is green and environmentally friendly.