The clinical significance of the chaotic dynamics in the cardiovascular system had attracted attention. Circulation system is a kind of "complex system" having many feedback circuits. So, it was very difficult to investigate the origin of chaos in the circulatory system. In this study, we investigated the origin of chaos by the use of the methodology of the open loop analysis with an artificial heart, which did not have any fluctuation in their own pumping rate and contraction power, in the chronic animal experiments using healthy adult goats. As a result, in the circulatory time series data of the artificial heart, which did not have any fluctuation, low dimensional deterministic chaos was discovered by the methodology of nonlinear mathematical analyzing technique, suggesting the importance of the blood vessel system in the chaotic dynamics of the cardiovascular system. To investigate the origin of chaos furthermore, sympathetic nerve activity was directly measured in the animal experiments with artificial heart circulation. Chaotic dynamics was also recognized in the sympathetic nerve action potentials, even during artificial heart circulation, suggesting the importance of a central nervous system. In the next step, in order to generate the chaotic dynamics in circulation, electrical simulation model of a left heart circulation with a feed back loop with some delay were tested and we found that we can make chaos in circulation by the feedback loop. Thus, we had constitute the artificial baroreflex system with an artificial heart system and found that we can make chaos in animal model. And finally we proposed the clinical application of these methodology for the diagnosis of an autonomic nervous system and found that it may be useful. These findings may be useful for analyzing the nonlinear dynamics in circulation.