According to the characteristics of asphalt material of anti-cracking layer in pavement structure and the shortage of existing research, adopting thermoplastic styrene-butadiene rubber ( SBS ) , crumb rubber modifier (CRM) and dibutyl phthalate (DBP) as modifier, a composite modified asphalt suitable for pavement structure anti-cracking layer is developed. Through the test of ductility, penetration, softening point and elastic recovery, the reasonable dosages of modifiers are determined. By dynamic shear theological test, viscosity and me...