The invention provides a fiber bragg grating type sensing system and a fiber bragg grating type sensing method for simultaneous measurement of temperature and strain. The fiber bragg grating type sensing system comprises a detection light branch circuit, a feedback detection branch circuit, a polarization-maintaining optical coupler, a modulation unit and a calculation unit, wherein the detection light branch circuit outputs double-sideband intensity-modulated detection light which is input to a sensing grating so as to achieve detection of transmission peak centers on a fast axis and a slow axis of the sensing grating; a reflection signal of the sensing grating is input to the feedback detection branch circuit through the polarization-maintaining optical coupler; the modulation unit outputs a frequency signal to the detection light branch circuit according to a control instruction and reading of the calculation unit; and the calculation unit corrects frequency parameters of the modulation unit according to data provided by the feedback detection branch circuit, so as to lock two sidebands of the detection light on corresponding transmission peaks of the sensing grating and calculates to obtain the temperature and the strain. The fiber bragg grating type sensing system and the fiber bragg grating type sensing method can significantly increase sampling rate and measurement resolution of the temperature and the strain, and achieve higher demodulation precision.