Wearable devices have great application potential in the next generation of smart portable electronics, especially in the fields of medical monitoring, soft robotics, artificial intelligence, and human-machine interfaces. Piezoelectric flexible strain sensors are key components of wearable devices. However, existing piezoelectric flexible strain sensors have certain limitations in weak signal monitoring due to their large modulus and low sensitivity. To solve this problem, the concept of Kirigami (paper-cutting) was introduced in this study to design the sensor structure. By comparing the Kirigami structures of different basic structures, the serpentine structure was determined as the basic configuration of the sensor. The serpentine structure not only provides excellent tensile properties, but also significantly improves the sensitivity of the sensor, which performs well in monitoring weak signals. On this basis, the adhesion properties of the flexible sensor were analyzed and tested, and the optimal ratio of the substrate was selected for preparation. In addition, a low-cost and rapid prototyping process for stretchable patches was established in this study. Using this technology, we prepared the sensor device and tested its performance. Finally, we successfully developed a flexible sensor with a sensitivity of 0.128 mV/µɛ and verified its feasibility for wrist joint motion monitoring applications. This result opens up new avenues for the recovery care of tenosynovitis patients after surgery.