Flexible tactile sensors are easy to fit irregular surfaces such as the skin. Compared with the rigid sensors, they have better signal perception ability, higher accuracy and better wearing comfort. Therefore, they play an important role in human-computer interaction, medical equipment, wearable devices, health monitoring and other fields. This review systematically introduces and compares flexible tactile sensors that categorized by different principles, analyzes sensor performance optimization methods from the perspective of structural optimization, and sorts out three common methods in electromagnetic-based principles: microstructure, structure loosening and multi-modal measurement. This review also summarizes applications in the field of medical rehabilitation robots, sorts out four specific application scenarios of robot control, human-computer interaction, medical equipment and physiological information monitoring, analyzes the different performance requirements of different application scenarios. For example, robot control requires high precision and short response time, human-computer interaction requires large area, multi-modality, etc. The relationship between structural optimization design and application is also given. Finally, this review briefly introduces the flexible tactile sensor information extraction, information fusion and other intelligent information processing methods, and prospects the development trend of the flexible tactile sensor.