A wavelength demodulation system combined wavelength scanning with time division multiplexing for fiber Bragg grating(FBG)array is proposed. Wavelength demodulation for a large capacity FBG array with a tree topology structure is realized by the pulse modulation of the optical signal with a wavelength scanning. The FBG array wavelength demodulation system is is built and the ability of wavelength demodulation for FBG arrays with a high degree of reusability is verified. The permanence of the wavelength demodulation for FBG array is tested. The experimental results show that this system can achieve the identification and demodulation of the wavelength for the FBG in each subarray with the wavelength accuracy of 2.5 pm and the fluctuation range is within ±2 pm.