The large amounts of municipal sludge are generated from waste water treatment plants.The organic compounds in sludge are helpful for methane production. While the most of municipal sludge in China is of low organic matter. Thus this paper explored the effect of different additive agents combined with thermal hydrolysis on organics solubilization of sludge with low organic and subsequent anaerobic digestion. The results showed that additive combined with low temperature thermal hydrolysis is helpful not only for the dissolution and the production of organics

including soluble sugar

soluble protein and TVFA(total volatile organic acids) but also for anaerobic digestion. The effect of organic dissolution under the thermal pretreatment condition(the solid content

the temperature and the time were 8%

90℃ and 24 h

respectively) and the additive concentration[the concentration of NaOH

Ca(OH)2 and CaCl2 were 0.018 g·(g DS)-1

0.016 g·(g DS)-1 and 0.0375(g·g DS)-1

respectively] was arranged in descending order

which were NaOH

Ca(OH)2 and CaCl2 in turn

namely the addition of NaOH had obvious effects on soluble sugar

soluble protein and TVFA

and the concentrations were 3051 mg·L-1

10686 mg·L-1 and 5740 mg·L-1 respectively. The ranking of efficiency of anaerobic digestion was NaOH

CaCl2 and Ca(OH)2 in turn

and the maximum gas production was acquired and up to 101.9 ml·(g VS)-1 with the addition of NaOH.