The invention discloses modified asphalt which comprises the following components in parts by weight: 75-95 parts of matrix asphalt, 1-10 parts of star-shaped SBS, 1-5 parts of waste rubber powder, 1-5 parts of waste plastic, 1-4 parts of a cross-linking agent, 0.8-1.5 parts of a compatilizer, 0.5-1.2 parts of kieselguhr, 0.5-0.8 part of nylon fiber, 0.3-0.7 part of carbon black, 0.3-0.5 part of talcum powder, 0.1-0.3 part of a stabilizer, 0.2-0.1 part of zinc oxide and 0.01-0.04 part of an ester solvent. The invention further provides a preparation method of the modified asphalt. The modified asphalt which is prepared by using the preparation method that different components are matched is good in high-temperature stability, low-temperature anti-cracking property and anti-fatigue property, relatively high in softening point and relatively good in adhesion property.