The invention belongs to the technical field of synthesis of organic silicon compounds, and discloses a preparation method of tetramethyl divinyl diphenyl trisiloxanae. The preparation method comprises the following steps: stirring at room temperature, dropwise adding 1,1,3,3-tetramethyl-1,3-divinyl silazane into a mixed dispersion solution of diphenyl silanediol and n-heptane, heating to 90 to 120 DEG C, continuously stirring for 2 to 4 hours, decompression rectifying, intercepting 1mmHg of fraction at 140 to 144 DEG C, and obtaining the tetramethyl divinyl diphenyl trisiloxane. By adopting an anhydrous system reaction, the situation that the diphenyl dichlorosilane or dimethoxydiphenylsilane serving as raw material is easy to have hydrolysis and condensate into a polymer in the water system can be avoided. The 1,1,3,3-tetramethyl-1,3-divinyl silazane has high alkality and can have self-catalytic reaction without additional catalyst. The invention provides the preparation method of the tetramethyl divinyl diphenyl trisiloxane which is simple in process, stable in quality and high in yield.