Several new bounds for the correlation functions of de Bruijn sequences are derived.It is shown that the set of all primitive de Bruijn sequences have the following two properties:1)for each sequence a in the set with large span n,the magnitude of its auto-correlation funct-ion|r(k)|is relatively small compared with the peak 2~n for all k≠0 mod 2~n;2)for each pair of sequences a,b in the set with large span n,the magnitude of their cross-correlation function |r(k)| is relatively small compared with the peak 2~n for all k.Some generalizations of the result are also presented.