The present invention relates to a needleless drug-injecting system and a drug-injecting method thereof, wherein the needleless drug-injecting system comprises a controlling device and a needleless drug-injecting device. By using the needleless drug-injecting system and the drug-injecting method, a user is able to individually set a variety of parameters comprising usage dose of liquid medicine, shot pressure of liquid medicine, air flow rate, single-shot quantity of liquid medicine, continuous shot frequency of liquid medicine, and a continuous shot spacing time according to different liquid medicine. Thus, after setting the parameters, the liquid medicine can be injected into the dermis layer of the face skin of a human when the user using this needleless drug-injecting system to inject any one liquid medicine to the human face, therefore the liquid medicine would be absorbed by the face skin without hurting the human face.