To improve the capability and detection precision of the fiber Bragg sensing system, the novel interrogation technique and a fast wavelength detection algorithm are proposed for the multi-channel fiber Bragg grating (FBG) sensing system. With the combination of the numerical simulation and experiment, it is demonstrated that the average precision of interrogation is 2 pm and the resolution is 0.1 pm over the working range of 1525～1585 nm. The system can realize the real-time monitoring of 32 channels more than 1000 sensors. Present work shows that the algorithm described in this paper can reduce the signal noise ratio (SNR) at the input of the system which influences the precision of interrogation. Compared with traditional wavelength detection algorithms, this interrogation method is greatly improved in measurement precision, wavelength range and working reliability. It can well be applied to practical engineering applications.