In order to analyze sequences, the minimum periodicity of sequences may be calculated. According to the relation of the sequence with its autocorrelation, an algorithm was brought forward. The periodicity of autocorrelation is equal to the periodicity of the digital sequence. The minimum periodicity of autocorrelation sequence is the position difference between the top apex with the second apex of the unitary autocorrelation excluding direct component. The algorithm principle was introduced and applications were afforded to verify the method. The result shows that the method was right to evaluate minimum periodicity of sequences successfully. The algorithm is helpful to analyze the periodicity of digital sequence.