Integer wavelet transform (IWT) and IWT-Based image-compression offer many advantages over traditional wavelet. But every subband coefficients of the IWT-Image have smaller dynamic change value and worse energy compaction than the first generation wavelet. Those reduce efficiency of embedded zerotree wavelet (EZW) coding. This paper proposes "integer square quantization threshold from 1" instead of "2 of integer power quantization threshold" during EZW coding. It shortens the distances of every quantization threshold, reduces probability of the important coefficients in the lower quantization threshold area and increases zerotrees. It reduces the coding signs and does not code the zerotrees of the most high-frequency subbands. The experiments results show that integer square zerotree wavelet (ISZW) coding algorithm solves the low efficiency of EZW based on IWT and improves the performance of compression algorithm. It may be used in still picture compression and transmission.