Sentinel lymph node biopsy is important in the early stage breast tumor resection surgery. Its results will determine if the axillary lymph node dissection (ALND) will be conducted afterwards. For locating sentinel lymph nodes, indocyanine green (ICG) has been widely used with a near infrared (NIR) camera to image its fluorescence. However, surgeons need to watch a screen beside the operating table to see the fluorescence, with their hands operating on the surgical site. We developed a navigation system that projects the invisible fluorescence back to the surgical site visibly in real-time. The system introduces a co-axial optics design to guarantee the projection accuracy. Phantom experiments are conducted to assess the projection resolution and accuracy of the system. Animal experiments with three mice show a good system performance and its preclinical feasibility. Furthermore, the system is tested in a clinical trial of ninety breast cancer patients in three hospitals in China. ICG and methylene blue (MB) is subcutaneously injected separately into the areola at 3-4 points to get both fluorescent and visible contrast, for further comparison. The navigation process is compared with a commercialized NIR imaging system. The results show a 100% detection rate of sentinel lymph nodes and a good consistency with the methylene blue and the commercialized imaging device. The experiments demonstrate good clinical feasibility of the co-axial projection system.