A spectrally confined Fourier domain mode-locked fiber laser which provides an optical gain amplification mechanism for normal operation of the laser through an optical gain module, An optical annulator couples saturable absorbers, saturable absorber can realize self-starting mode-locking of laser, At that same time, so as to obtain ultrashort laser pulse, By means of polarization controllers, bychanging the local polarization state of the internal optical path of the laser, By introducing dispersion management delay module, A dispersion management mechanism can be provided for the inside ofthe laser resonator, At the same time, the frequency of wavelength scanning driving signal is set to match with the resonant frequency of laser cavity, so that the wavelength scanning module of Fourier domain mode-locked laser cavity can pass through again exactly when the scanning wavelength laser passes around the cavity and returns to the wavelength scanning module. The mode-locked fiber laserof the invention can realize the advantages of high wavelength scanning frequency, narrow pulse linewidth, ultrashort laser pulse width and the like.