The invention discloses functional organosiloxane containing asymmetrical substituted urea and a preparation method thereof. The preparation method comprises the following steps: carrying out reaction between 4, 4'-dibromodiphenylamine and triphosgene to obtain (i) N, N(/i)-di(4-bromo phenyl) carbamyl chloride; and then, carrying out reaction with 3-aminopropyl triethoxysilane to obtain functional organosiloxane, wherein the organosiloxane is the functional organosiloxane containing asymmetrical substituted urea through the verification of infrared spectrum, ultraviolet spectrum, 1H-NMR (1Hydrogen-Nuclear Magnetic Resonance) and 13C-NMR. The structure of the compound contains a plurality of functional groups such as siloxane, amide, urea groups and bromoaryl. The functional organosiloxane has a potential application value on the respects of molecular imprinting recognition materials, structural flame retardant materials, rare earth light emitting materials, white carbon black and the like. The functional organosiloxane disclosed by the invention is reasonable in synthetic line, mild in condition, easy to operate, low in cost of raw materials and high in product yield.