An embedded block wavelet coding method based on block bit-length is put forward for resolving the problem of occupying a large amount of memory in coding process for a wavelet coder.The memory occupancy can be reduced and coding efficiency can be improved through four measurements in the coding process.The four measurements mentioned above are:(1) LL_n sub-band is separately coded;(2) Block bit-length chart in terms of bit-length defined by the author is established;(3) The space of memory is saved by employing bit-length chart instead of fining lists and ranking processes;(4) The key blocks are searched by constructing bit-length chart to overcome the repeat scan and to improve the coding speed.The software experimental results show that for a piece of 512 pixel×512 pixel×8 bit image,occuping memory space by proposed method is 1/27 that of SPECK,the performance of radar image derived from hardware test can satisfiy the international standard.Meanwhile,proposed method can keep the high quality of PSNR and can be implemented through hardware easily.