A scheme of fiber Bragg grating(FBG) wavelength demodulation based on tunable Er-doped fiber ring laser is proposed and demonstrated.The narrowband filter of the ring laser consists of the sensor FBG and the tunable FBG of which the Bragg period is tunable through a one-dimensional adjustor.The one-dimensional adjustor,which is connected with a step motor that is controlled by a programmable logic controller(PLC),can control the transmission of the filter,which decides the character of the laser output.The tuning module,the O/E circuit,the detecting-and-controlling system and the ring laser construct a close loop,which performs the wavelength demodulation.The experimental results show that the precision of the proposed system is about 0.02 nm in a range of 4.04 nm.