According to the coding process of MPEG-4 VCT,coding-decoding frame of VTC consistent with standard of MPEG-4 is presented. The problem of scalable MPEG-4 VCT BQ image coding is investigated from the viewpoint of consistency of zerotree symbol with the objective image of bit-stream layer. An improved PEZW algorithm, SP-PEZW is presented. The experiment of the color Lena image is researched applying to SP-PEZW. Experiment results show that PEZW algorithm comparing with the bitrate of low resolution bitstream layers of SP-PEZW algorithm is lower, while bitrate of the highest resolution bitstream layer is the same, and image of the highest resolution spatial layer which is decoded at the special bitrate is better.