In recent years, soft robots have become a research hotspot due to their smooth motion characteristics and safe human-robot interaction. Unlike traditional rigid robots, the low stiffness and large deformation kinematic characteristics of soft robots make it relatively difficult to control them accurately. In this paper, a rigid-soft-coupled continuum arm(RSCCA) is designed based on pneumatic muscle drive, which combines the flexibility and safety of a soft robot with the stability of a rigid robot. In series, the RSCCA comprises three modularly designed rigid-soft-coupled joints(RSCJ). We installed joint angle sensors in the rotating joint part of the skeleton, which can monitor the motion state of the skeleton in real-time. Finally, we carried out a closed-loop PID control for the RSCJ based on the joint angle information. The experimental results show that the RSCCA can be closed-loop controlled according to the joint sensing information.