Autocorrelation-based velocity measurement is studied with self-mixing speckle in an erbium-doped ring laser. The autocorrelation function of self-mixing speckle is deduced using the optical feedback theory of fiber ring laser, and a relation between the autocorrelation frequency of speckle signals and the velocities of moving object is theoretically obtained. Utilizing the experimental system based on an erbium-doped fiber(EDF) ring laser, the velocity measurement is carried out toward a dynamic target with different velocities. Linear relationship between autocorrelation frequency and the velocity of the target is proved. The result indicates that the autocorrelation of self-mixing speckle in a fiber ring laser can be applied to velocity measurement.