The invention relates to high-viscosity organosilicon elastic glue mud for buffers and a preparation method of the high-viscosity organosilicon elastic glue mud. The high-viscosity organosilicon elastic glue mud is methyl phenyl organosilicon elastic glue mud with the viscosity of 6.0*105-1.5*107 mPa*s. The preparation method comprises the steps of conducting ring opening polymerization with a traditional basic catalyst, adding an appropriate amount of catalyst and chain stopper, allowing methyl cyclosiloxane and phenyl cyclosiloxane to conduct the ring opening polymerization till a system is transparent, adding an appropriate amount of catalyst to proceed reaction, and obtaining the transparent methyl phenyl organosilicon elastic glue mud and the high-viscosity organosilicon elastic glue mud. The preparation method is simple in process and convenient to operate, the transparent high-viscosity methyl phenyl organosilicon elastic glue mud can be prepared, and the preparation method is particularly more important in preparing the high-viscosity elastic glue mud with glass-transition temperature of approximately -120 DEGC. The high-viscosity methyl phenyl organosilicon elastic glue mud is applicable to the buffers of draw gears of a railway coach and a railway wagon, and the buffers of military and civil heavy mechanical equipment.