The invention discloses a rubber modified asphalt warm-mixing agent, a preparation method and application thereof. The warm-mixing agent comprises the following components in parts by weight: 100 parts of water, 5-30 parts of fatty alcohol sodium sulfate, 15-30 parts of palmitic acid, 5-30 parts of oleic acid, 1-20 parts of sodium dodecyl benzene sulfonate, 1-15 parts of cetyltrimethylammonium chloride and 10-30 parts of imidazoline-type cationic surface active agent ODD. The preparation method comprises the following steps of: adding the water in a container at the temperature of 65 DEG C, and then adding the following substances under the condition of stirring: the fatty alcohol sodium sulfate, the palmitic acid, the oleic acid, the sodium dodecyl benzene sulfonate, the cetyltrimethylammonium chloride and the imidazoline-type cationic surface active agent ODD, and stirring for 15 min to obtain the warm-mixing agent. The warm-mixing agent is directly applied to rubber asphalt or matrix asphalt to reduce the viscosity of the asphalt. The kinematic viscosity of the rubber powder asphalt added with the warm-mixing agent at the temperature of 150 DEG C can reach less than 3.0Pa.s of the kinematic viscosity at the temperature of 180 DEG C, and the production temperature can be reduced by about 30 DEG C, thereby not only preventing the rubber asphalt from being aged but also savingenergy and reducing equipment loss.