In order to solve the defects of the flexibility, adaptability and the safety of human-computer interaction of the arm joint of the service robot, an antagonistic rotary joint with buffer capability was developed by using the self-developed rotary driver. It consists of two groups of arc-shaped pneumatic artificial muscle drivers and the middle pneumatic brake with 180 degrees difference in the same installation phase, in order to avoid interference between the two groups of drivers, the two groups of pneumatic artificial muscle drivers are pre injected with 0.12Mpa air pressure, and the joint rotation function is realized based on the antagonistic principle, and the joint position and posture maintenance function is realized by the cooperation of pneumatic brake. The experimental results show that by controlling the gas pressure of the actuator, the rotation direction and the output driving force of the joint can be adjusted accurately; the rotation angle and output torque of the joint are proportional to the pressure difference between the two actuators. When the two actuators are filled with the same air pressure, the joint angle is 0 °, the rotation torque is 0; when the pressure difference between the two actuators is 0.24Mpa, the maximum joint angle is 60.5 °, the maximum rotation torque is 4.76N.m.