The invention discloses special rubber powder for a non-cured rubber asphalt waterproof coating and a preparation method thereof. The special rubber powder is prepared from, by weight parts, 50-65% of tire rubber powder, 20-40% of butyl rubber powder, 0.1-1.5% of activator, 0.1-1.0% of viscosity reducer and 5-15% of separant. The preparation method comprises the following steps: 1) stirring the tire rubber powder and the butyl rubber powder; 2) heating the activator and spraying the activator to the rubber powder obtained in the step 1), and then performing stirring and pre-activation; 3) mixing the pre-activated rough rubber powder obtained in the step 2) with the viscosity reducer and the separant, forming fine rubber powder through grinding, sieving the fine rubber powder, and performing packaging to obtain the finished product. Through the compounding of the waste tire rubber powder and the butyl rubber powder, the performance can meet the creep property, cohesiveness, self-healing property and ageing resistance requirements of the non-cured rubber asphalt waterproof coating. The added amount of plasticizer and polymerization modifiers is reduced effectively, and the cost can be reduced by over 10%.