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Body temperature is an important indicator of human health detection which can reflect the key information of human life activities. The real-time and accurate monitoring of skin temperature can reflect the health status of the human body for timely intervention and treatment which plays an important role in daily protection and clinical medicine. Conventional contact thermometers are easily to be misplaced during measurement due to poor fit with skin which affects normal human activities. The infrared thermometers without directly contacting the skin can measure the temperature fast but due to the easy shift of the infrared head in the measurement process the skin radiation level and the environmental factors will affect its measurement accuracy. The paper or film-based temperature sensors are flexible and lowly breathable so they are not suitable for dynamic measurement of human body temperature or real-time monitoring of single point skin temperature. Temperature sensing yarns combine a hybrid electronic yarn with microscopic sensing elements and flexible textile fibers which endow them with good feel and comfort to measure single point skin temperature and dynamic human body temperature. In order to know well the development status and trend of temperature sensing yarns and promote their industrial application we firstly analyzed the sensing characteristics of typical temperature sensing yarns i. e. thermoelectric temperature sensing yarns optical fiber temperature sensing yarns and thermal resistance temperature sensing yarns. Among them four methods for preparing thermistor sensing yarns were mainly introduced hybrid spinning filament dipping coating of textiles flexible printing electronics and flexible hybrid electronics. Then we summarized the characterization parameters and influencing factors of these temperature sensing yarns in terms of sensing properties and working performance. In the end we presented the technical challenges and shortcomings of temperature sensing yarns in industrialization and application. It is found that thermoelectric temperature sensing yarns can generate electricity according to the temperature difference between human body and cold environment but the compensation problem of cold end needs to be solved. Optical fiber temperature sensors with high measurement accuracy and anti-electromagnetic interference are settable. Thus they can be used as yarns to manufacture smart textiles. However they are easily broken under mechanical stress in service. Thermal resistance sensing yarns are difficult to locate and their accuracy is easily affected by the surrounding humidity or sweat so further improvement is needed for long-term local temperature measurement on human body. Thermistor sensing yarns are suitable for the medical field because of high sensitivity but they have poor durability and washing ability. At present there is no in-depth study on the mode and mechanism of yarn function failure and no systematic design principle to guide large-scale production. Temperature sensing yarns which boast the advantages of softness comfort and invisibility are suitable for smart textiles to measure human temperature such as socks for predicting early diabetic foot ulcers clothing and bedding for continuous temperature measurement of infants bandage for monitoring wound infection and so on. The summarized characteristics of various temperature sensing yarns provide suggestions for the evaluation criteria structure optimization and functional failure theories of sensing yarns as well as the future application and selection of smart textiles. [ABSTRACT FROM AUTHOR]