This paper presents a design scheme for a novel rigid-flexible hybrid robotic arm. The robotic arm consists of a two-section bellows flexible section with a hybrid drive including pneumatic and tendon cable drives, and a motor-driven rigid section. This design aims to maintain the high flexibility and safety of the flexible arm while enhancing the load capacity and rapid response characteristics of the robotic arm. Its highly integrated design allows for modular installation on various types of robots, thereby adapting to diverse operational requirements in different environments. The robotic arm features a unique flexible structure facilitating smooth transition between the rigid and flexible sections. The hybrid drive design allows the flexible part to gain the ability to change stiffness and flexibly change postures while maintaining high stiffness. In the paper, we propose an improved PCC (Piecewise Constant Curvature) model for the flexible arm and establish kinematic models for each part of the robotic arm, enabling flexible control and validating the structural rationality, thus offering new insights for the design of robot arms.