The thermophilic (55℃) anaerobic digestion were conducted in order to investigate the constituents of extracellular polymeric substances (EPS), such as proteins and polysaccharides, and the influences of EPS on dewaterability of thickened sludge with humus soil (HS) or not. EPS were divided into two states i. e. dissolve-EPS and bound-EPS by centrifuge and heating respectively. During the whole process, dissolve-EPS, bound-EPS and Capillary suction time (CST) were detected. Results show that CST during digestion was markedly higher than the raw sludge. Statistical analysis suggest that CST and dissolve-EPS had a positive correlation; CST and bound-EPS had a negative correlation. After 21 days, dissolve polysaccharides in sludge with HS was less than without HS about 7% . However, dissolve proteins, bound-EPS did not have difference obviously in sludge. CST of sludge with HS was less than other about 25%. It indicates that dissolve polysaccharides had a strong influence of dewaterability of sludge.