Therapeutic use of ultrasound (US) has a great potential for minimally invasive therapy. We have studied acoustic microbubble delivery for effective sonoporation and thermal therapy. To apply the techniques in vivo, a navigation system for US field positioning is indispensable. To address this issue, we have developed an intuitive navigation system using augmented reality (AR) technology. The system consists of an optical tracking device, a linear US probe, a focused US field source (US transducer) with 2.0-mm focal spot, a USB video camera, and navigation software. The probe was calibrated accurately using US probe calibration technique. Also, the transducer was calibrated using a three-dimensional sound field measurement device. Finally, the camera was calibrated using a chess board. The system we developed provides two kinds of augmented information : 1) therapeutic US field visualization on echogram, and 2) echogram plane and sound field visualization on video frame. In this study, the respective calibration accuracies were validated and microbubble trapping experiments using the focused US transducer and artificial blood vessel with 2.0-mm diameter were conducted. In the experiments, microbubbles were trapped inside the artificial blood vessel using the navigation system, implying that the focus position could be located in the blood vessel. The results demonstrated that the system we developed has adequate accuracy for microbubble control in 2.0-mm blood vessels.