In this paper, given a q-ary LCZ sequence set with parameters (N,M,L, ǫ) and even q, we construct another q-ary LCZ sequence set with parameters (2N, 2M,L, 2ǫ) when q is even. Especially for odd L such that L|N , if a q-ary optimal LCZ sequence set with parameters (N,M,L, 1) is used, the new set with parameters (2N, 2M,L, 2) can be optimal in terms of the set size.