Improved needle-free injection device can be faster in the selection of piston pressurized water jet injection modules, and the replacement of the venturi tube atomizing injection module and liquid contained can

The present invention provides an improved needle-free injection device, which is characterized by including a pop-up type nozzle cover that can help to quickly disassemble and replace the venturi tube atomizing injection module and the medicine can; a replaceable piston pressurized water jet injection module; a replaceable limited microporous sheet; an eccentric flow-through slot for improving the biological material in the liquid contained can to enter the venturi tube atomizing injection module; a fixed member with a movable axis and a fixed seat that can quickly replace the venturi tube atomizing injection module and prevent the separation during the operation process; and a detachable handle including a built-in power source and a gas source. This assembly can enhance the function of the needle-free injection device in the user-friendly operation, and can achieve the effect of quantitatively outputting atomized liquid medication more efficiently and stably. Moreover, the needle-free injection device has