Balloon aortoscopy is a technique for viewing inner wall of aorta and used in clinics [1, 2]. By this method, endoluminal aortic surface could be clearly monitored, however, during this period, the aortic blood flow is blocked off by the inflated balloon. To solve this clinical problem, we have been developing a prototype aortoscope system without blocking off aortic flow aiming for the use of an assistive technique for endovascular interventions such as stent-graft placement for aortic aneurysm and have been evaluating through in vitro and in vivo tests. The technique introduced for this purpose was the use of intermittent and instantaneous saline jet controlled by a high-speed electromagnetic valve synchronized to heart beat (diastolic phase). In the previous study, we designed an endoscope with two channels (one for saline discharge and the other for forceps insertion), and confirmed the validity of this method by in vitro and in vivo tests [3, 4]. Based on these findings, in this study, we have newly designed a conventional and low price endoscope system aiming for wide clinical use. From the results of in vitro tests using a mock circulation system, it was confirmed that the newly designed system was capable of visualizing a target installed on an inner surface of the mock system suggesting an availability of the system for an aortoscope without blocking off aortic flow.