Objectives Most medical instruments are designed for diagnosis purpose but very few for clinical treatment. Our research aim is to design and develop a cardiovascular automatic feedback control instrument (CAFCI) for rescuing the critical patients with abnormal blood pressure.Methods The CAFCI was designed on the basis of abundant clinical experiences and on successful mathematic modeling of our experimental data. The blood pressure, pulmonary capillary wedge pressure,and rates of heart beat were measured and inputted into a computer and drugs were chosen by a doctor through a user-friendly interface with the computer.The responses to medication were rapidly acquired and feed back to the computer by automatic detection system in a close-loop system. The data were refreshed every 7.5 sec in order to regulate the speed and dosage of the medications that were given. Results The experimental results with ten dogs showed that the CAFCI system took samples promptly and accurately so that the targeted blood pressure could be reached reliably based on our input parameters and our designing requirements. Conclusions Since the dependability and accuracy of the CAFCI system are much superior to that of the traditional method, its clinical application to rescue the critical patient warrants evaluation in the future.