As the technology of WDM is practicality, the wavelength tunable laser becomes the key component of WDM. Then it is important to optimize its property and simplify its structure. In this paper, a new type of laser structure by using EDFA (Er3+-Doped Fiber amplifier) and AOTF (acousto-optical tunable filter) is demonstrated. Theorilly, the output characteristic of such laser is analyzed, as the same time, the factor which effect the output characteristic of laser is also analyzed. Base on the analysis, some method to improve the properly of laser are proposed.