This paper introduces a novel robotic gripper, named as the SPD gripper. It features a palm and two mechanically identical and symmetrically arranged fingers, which can be driven independently or by a single motor. The fingertips of the fingers follow a linear motion trajectory, facilitating the grasping of objects of various sizes on a tabletop without the need to adjust the overall height of the gripper. Traditional industrial grippers with parallel gripping capabilities often exhibit an arcuate motion at the fingertips, requiring the entire robotic arm to adjust its height to avoid collisions with the tabletop. The SPD gripper, with its linear parallel gripping mechanism, effectively addresses this issue. Furthermore, the SPD gripper possesses adaptive capabilities, accommodating objects of different shapes and sizes. This paper presents the design philosophy, fundamental composition principles, and optimization analysis theory of the SPD gripper. Based on the design theory, a robotic gripper prototype was developed and tested. The experimental results demonstrate that the robotic gripper successfully achieves linear parallel gripping functionality and exhibits good adaptability. In the context of the ongoing development of embodied intelligence technologies, this robotic gripper can assist various robots in achieving effective grasping, laying a solid foundation for collecting data to enhance deep learning training.