In this paper, we use three-dimension lattice vector Z3 to design an index assignment for three-channel multiple description coding. In the labeling procedure, the side quantizers are based on the sublattice, but the central quantizer is not only based on the lattice but also combines some spheres to get a better tradeoff between the central distortion and side distortion. Then this scheme is used on wavelet image coding. The experiment results on gauss source and standard test image both show that this scheme is simple and effective.