Based on the investigation of EZW

the relationship between space redundancy(scaled by edge active measure) of the compressed image and the result of EZW coding is analyzed

and the concept that there exists an optimal wavelet decomposition level in EZW is proposed.The relationship in EZN coding between different compression ratio

different decomposition level and different images is reported.The executing time is also used as a factor for selecting decomposition level.The experimental results indicate that the three-level decomposition in EZW should be adopted for high compresssion ratio and the four-level decomposition is optimal for low ratio.The results provide a basis for further research on adaptive EZW algorithms.