The shape memory alloy (SMA) is increasingly utilized among many industrial and civil applications as it is small in size but mighty in output. However, most of the current SMA-based mechanisms face with the low controllability or bulk dimension. In this paper, a novel flexible SMA wire-based gripper is developed to address these challenges for improving the clamping stability and stroke for confined operation. To achieve this, the long SMA wire was spaced smartly within a miniature space to increase the output, further, to improve the stroke of the gripper (14 mm vs conventional 2 mm). Then, the theoretical model of the system was established by considering the thermal effect of SMA material and the static performance of the flexible beams. After that, the experimental setups were prototyped to crossly test the performances of the proposed SMA gripper. It can be seen from the experimental results that the model presented in this paper can be validated with high accuracy (error: 3.4%). It can also be found that the SMA gripper can realize the high tracking performances (i.e. 8.9% accuracy in displacement step response, 10.8% in displacement tracking response, and 12.1% accuracy in clamping force tracking response, respectively) for the industrial applications.