A liquid-powder drug prompt-mixing type automatic syringe includes an injecting assembly, a drug-mixing assembly and a shooting device. The injecting assembly includes an injecting outer sleeve, in which the mouth of a blocking ampoule is slidably socketed, a needle is coaxially connected to the blocking ampoule by a hub; the drug-mixing assembly includes a drug-mixing outer sleeve, in which a precharging pressure menstruum bottle by a drug-mixing needle bracket; the shooting device includes a shooting outer sleeve and a spring pushing rod mechanism slidably socketed in the shooting outer sleeve a movable joining mechanism allows the injecting assembly to alternatively connect the drug-mixing assembly and the shooting device respectively. A liquid drug automatic syringe includes said injecting assembly and the shooting device.