The stability of strain sensors has always been a concern in the domestic sensor industry and engineering testing industry. There are many indicators of strain sensors, and there is no simple mathematical relationship between the indicators, so the long-term stability of sensors cannot be studied in a general manner. In this paper, the working principle of strain sensor is given, and the essential reasons for the instability of strain sensor are discussed from the aspects of Strength of materials, quantum mechanics and electronic mechanics, and the common methods to improve the instability of Strain gauge are summarized. The discussion in this article has certain reference value for the design and engineering application of strain sensors