This paper presents the design and pilot experiment of a novel full-drive decoupled bionic finger with four degrees of freedom (DOFs). Each joint of the proposed finger can operate independently, without interference from its company. Three pneumatic artificial muscles and a steering engine serve as the drivers for all the four joints, which ensures their independent motions. More specifically, the pneumatic artificial muscles drive the distal interphalangeal (DIP), middle interphalangeal (MIP) and proximal interphalangeal (PIP) joints, who can realize flexion. The steering engine drives the metacarpophalangeal (MP) joint, which performs the adduction and abduction motion. Tendons transfer power from the pneumatic artificial muscles and drive the front three joints with compliance. Different from the traditional tendon drive systems, we proposed a new N type tendon drive scheme, which enables the decoupling between the joints with just one single tendon driving single joint. The MP joint is driven separately by the steering engine and has no influence from other joints. With the characteristics of full-drive and decoupling, the bionic finger has less demand for sophisticated mathematical model and control algorithm, and can achieve precise position and orientation through relatively simple controller. Finally, the motion and grasping experiments demonstrated the full-drive and decoupling features, which implies the possibility for future application in dexterous hand development and practice.