The invention discloses a sensing method of a double-sideband filter demodulation-based dual fiber grating tension sensor, which belongs to the field of measurement of fiber grating sensors and aims to solve the problem of influence of light source power fluctuation on the demodulation precision of a sideband demodulation technology of the conventional fiber grating sensor. Wideband light emitted by a band light source is changed into transmitted light with double sidebands after passing through a double-sideband filter and then is divided into two beams of light by a first coupler, wherein a beam of light is reflected to a first photoelectric detector by a first fiber grating tension sensor after passing through a second circulator and the optical signal is converted into an electric signal by the first photoelectric detector, and the other beam of light is reflected to a second photoelectric detector by a second fiber grating tension sensor after passing through a third circulator and the optical signal is converted into an electric signal by the second photoelectric detector; data measured by the first photoelectric detector and the second photoelectric detector are acquired by a data acquisition device and are processed through a data processor. The double-sideband filter demodulation-based dual fiber grating tension sensor is applied to the field of optics.