The present invention relates to a preparation method for a linear or cyclic trisilaalkane which is a substance useful in the preparation of polycarbosilane and silicon carbide precursors. Linear or cyclic trisilaalkane and organic trichlorosilane derivatives can be synthesized simultaneously and in high yield by reacting bis(chlorosily)methane having a Si—H bond, either alone or together with an organic chloride, using a quaternary organic phosphonium salt compound as a catalyst. Further, since the catalyst can be recovered after use, the present invention is very economical and is thus effective for mass-producing precursors for organic/inorganic hybrid substances.