SPIHT algorithm is an embedded zerotree coding algorithm known for its high performance. However, it needs a large number of memories and many repeated calculations, so it is more complicated, and can′t implement real-time compression. The improved algorithm modifies the SPIHT algorithm by use of two concepts-minimum threshold and minimum exported bit, changing the original scanning order. Experimental results show that it reduces both the memory requirement and the time consumption, at the same time the PSNR value and human′s visual effect of the reconstructed image are close to SPIHT algorithm.