Abstract: The basic setup, main components and their functions of a fiber laser oscillator are briefly introduced, and the current development status of fiber oscillator is presented. The temporal, spatial and spectral properties of the oscillator are analyzed based on the Fiber Bragg grating(FBG). The mechanism, method and progress in manipulation of the central wavelength, linewidth and shape of the output of the oscillator are introduced. The mechanism, method and progress in manipulation of the output mode of the oscillator are introduced via the relationship between the eigen mode and the reflection spectrum. Recent progress of the instantaneous temporal property modeling is shown, the relationship between temporal and spectral properties and their influence on the nonlinear effect are revealed. Two kinds of cavity-free high power fiber lasers are briefly discussed.