Based on the good extensibility and conductivity, the flexible sensors (FSs) have a wide range of applications in the field of the electrochemical energy storage and variable stress sensors, which causes that the preparation of FSs also become a hot spot of research. Among the materials for preparing the FSs, the flexible carbon matrix composites (FCMCs) have become the widely used material since the good performance in the properties of electrochemistry and mechanics, which could be divided into three types: the carbon nanofibers (CNFs), the carbon nanospheres (CNSs) and the carbon nanotubes (CNTs). Compared with CNFs and CNSs, the CNTs wrapped by the polydimethylsiloxane (PDMS) have the advantages of the excellent extensibility and electrochemical stability. Therefore, the CNTs flexible sensor (CFS) could be well used in the field of the FSs. The purpose of this review is summarizing the preparation methods and application fields of CFS and proposing the research direction of CFS in the future. In this paper, two methods for fabricating the CFS have been designed by consulting the methods mentioned in the literature in recent years, and the advantages and disadvantages between the two methods have been explained. The application fields of CFS in recent years are enumerated, and the conclusion that the application fields of CFS are very wide is drawn. At the end of this paper, the review concludes with an overview of key remaining challenges in the application fields of the CFS.