As an important branch of medical robot, rehabilitaction training robot for hemiplegic upper limbs is a hot research topic. Based on motor relearning program, it covers many technology fields, such as rehabilitation medicine, human anatomy, mechanics, computer science, and robotics, etc. With the developing of auxiliary robot, there are still some disadvantages in the existent devices, such as heavy weight, few degrees of freedom, non-portable, low accuracy. These defects make it difficult for the rehabilitation robot to be applied to the actual rehabilitation practice. In this paper, we designed a rehabilitation robot with three DOFs. Compared to the previous device, this design can overcome some shortcomings which makes it flexible, portable, light weight, high accuracy and easy to wear. In this paper, the general structure of the flexible robot manipulator is introduced. The experiment is designed to test and analyse the error in its movement. The application of flexible transmission can greatly reduce the weight of the patient's arm, but may lead to errors in accuracy. Therefore, it is necessary to design experiments to test and analyse errors. The results show that the device can be easily and smartly dressed and has high accuracy.