The rapid development of robotics technology and human-machine interaction has created a growing demand for accurate and reliable three-dimensional force measurement. Flexible force sensors, known for their high sensitivity, bendability, and customizability, offer an effective solution for achieving accurate three-dimensional force measurements. This review aims to comprehensively assess the research progress of flexible force sensors in the field of three-dimensional force detection and explore their potential applications in various areas. Firstly, the working principles and structural characteristics of flexible three-dimensional force sensors are introduced. Then, the materials utilized by these sensors are discussed. After that, the decoupling methods of three-dimensional force sensors are summarized. Finally, the review summarizes the current applications of flexible three-dimensional force sensors in robotics, adjuvant therapy, human monitoring field, and controllers. By comprehensively analyzing existing literature and research results, this review offers important guidance for further advancing the application of flexible force sensors in the field of three-dimensional force detection. With the continuous development of technology, flexible three-dimensional force sensors are expected to increasingly play a significant role in the critical task of achieving accurate three-dimensional force detection.