Abstract: A device combining positioning and injection systems for injection within a body cavity, comprises: a tubular housing surrounding an accommodating space and having an opening hole fluidly connected to the accommodating space; a curved channel fluidly connected to the accommodating space and the opening hole; an injection needle disposed inside the accommodating space and the curved channel; the injection needle having a piercing portion penetrating through the opening hole and configured to extend outward from or retract inward into the opening hole; a plurality of ultrasonic transducers installed at the tubular housing and at two opposite sides of the opening hole; wherein at least one of the ultrasonic transducers being used to transmit a detection signal, and at least one of the ultrasonic transducers being used to receive the detection signal; a monitoring unit connected to the ultrasonic transducers via a transmission unit for information transmission therebetween.