Synthetic aperture radar（SAR）is an active microwave imaging sensor.It utilizes pulse compression technol- ogy to obtain high range resolution and aperture synthesis technology to achieve high azimuth resolution.SAR has a capa- bility of obtaining high resolution images that no ordinary radar can be comparable with

therefore

it is one of the signifi- cant directions for the modem radar development.The raw SAR data is difficult to be transmitted and stored due to its large size

so it is necessary to use data compression or reduction techniques.In this paper

based on the characteristics of SAR raw data coefficients in Walsh transform domain

an algorithm of variable bit rate allocation according to energey dis- tribution of every subband in Walsh transform domain-Block Adaptive Quantization in Walsh Transform domain（WHT- BAQ）is put forward.The comparison among WHT-BAQ algorithm

time domain BAQ algorithm and FFT-BAQ algorithm is conducted.By using two real SAR raw data

compression and decompression with the three algorithms are made respec- tively.The quality parameters are achieved

and the complexity of the three algorithms for raw SAR data compression are studied.The images correspond to the three algorithms are gained.The experiments manifest

due to bit allocation is introduced according to energy of different subband in Walsh transform domain

therefore

with same bit rate

SQNR and SDNR of WHT-BAQ algorithm surpass that of time domain BAQ algorithm.The increase of I.15-I.48dB is gained for SQNR

and the increase of 1.54-1.73dB is gained for SDNR.The performance of WHT-BAQ algorithm is comparable with FFT-BAQ algorithm.In different bit rate

the variance of resolution.PSLR and ISLR is small for the three algorithms. The above mentioned manifests

data compression technique（in the case of bit rate more than 2 bits/sample）hardly in- fluences resolution of SAR image hardly

and SAR image is not sensitive to bit rate of raw SAR data.The operation of WHT-BAQ algorithm is a little of exceed BAQ algorithm

but is much less than that of FFT-BAQ algorithm.In addition

as Walsh transform has the characteristics of fast speed algorithm and dose not need multiplication

therefore

WHT-BAQ algorithm has some advantages in the domain of SAR raw data compression.