Abstract: A new type of isokinetic muscle tone testing system was designed for the Parkinson's patients with dysmyotonia. The system consists of a mechanical device, a data acquisition unit, and a data processing and analyzing software. The mechanical device comprises an arm supporting device, a safety limiting device and a height adjusting device. Data acquisition unit, composed of a torque sensor module, a motor control module, a data communication module, and so on, is used to control the arm at constant speed and convert the sensor's analog signal into digital signal, then the signal is transmitted to the computer in real-time by USB interface. The data processing and analyzing software, developed by VC++, has finished the data processing, display, storage, generated the reports, et al. The experimental results show that this system is reliable and safe, not only can evaluate the degree of abnormal muscle tone in Parkinson's patients, but also can be used in the rehabilitation training of patients with dysmyotonia, which has strong expansibility.