The improved real time water absorption test device was used to realize the synchronous coupling of loading and water transport process. The capillary water absorption of high strength concrete(HSC)under short term sustained compressive loading was investigated. The influence of stress level on capillary water absorption property of HSC with granulated blast furnace slag(GBFS) contents of 0%, 10% and 20%was analyzed. The results indicate that within 0%60% stress levels, the accumulative water content and averaged water absorption rate decrease initially and then increase with increasing stress level. under the short term sustained compressive loading, the influence of load on the water absorption of concrete is mainly in the initial stage, and the change of water absorption caused by the content of GBFS is more significant in the later stage. The stress threshold for variation of capillary absorption property of grade C60 HSC is approximately 40% of its ultimate compressive strength,higher than