A stable mode locked fiber ring laser with large dispersion cavity is demonstrated. In this laser, the instability caused by cavity length excursion is suppressed. At the same time, the super mode noise is suppressed too. A 10 GHz mode locked erbium doped fiber ring laser using a large dispersion cavity developed, in which the pulse repetition rate is 10 GHz with sech 2 profile, the pulse width (FWHM) measured by autocorrelation meter is 7.6 ps, and the time bandwidth product is approximately 0.335.