SF6 density relays are widely used in high-voltage circuit breakers, high-voltage cables, high-power transformers, high-voltage transformers and other SF6 electrical engineering equipment to monitor and monitor the gas density of SF6 in closed containers. Adopting mechatronics technology, it has the functions of indicating value, contact and electrical signal and temperature compensation. The data collection and monitoring of SF6 gas density, temperature and pressure are realized. The risk of low gas density is prevented even under harsh conditions.