The invention discloses a pullulan based nano-drug carrier used for ultrasonic control release, a drug carrier system and a preparation method of the nano-drug carrier, and belongs to the technical field of biomateirals. 4-chlorobutyryl chloride and stearic piperidine ester are modified on a side chain of the pullulan successively through the acylation reaction and the coupling reaction of the free radical of nitroxide to prepare P-OC. The invention further discloses application of the ultrasonic control release carrier system, the P-OC is self-assembled in a water soluble environment to forma micelle structure, a hydrophobic anti-cancer drug is wrapped on an inner core, and the drug is controllably delivered in the space and time. The drug-loaded nano-micelle P-OC/DOX has a better effecton killing the cancer cell under the external ultrasonic condition, the effect on inhibiting the cancer cell is poor without the ultrasonic treatment, and the ultrasonic controllable release drug carrier system has a potential application value in the fields of sustained release of the drug and the treatment of cancers.