Using the novel distributed fibre sensing technology newly developed in recent years with fibre being taken as the medium of signal transfer and sensing and taking advantage of the sensitivity to temperature of the Raman effect of fibres and the theory of reflection of optical time-domain, SH97400 can make real-time measurement of the temperature distribution along the fibres. The measuring points may be up to 200^oC-500^oC per kilometer. The measuring accuracy may reach + 2^oC within the range of 0-150. The entire temperature curve and enlarged part theory of can be displayed. It has multiple functions including double limit alarming and self-inspection as well a series of advantages such as resistance to combustion, explosion, electromagnetic disturbance and corrosion, small volume, light weight, low power consumption and safe and reliable operation.