This study investigated the feasibility and performance of simultaneous in-situ CO2 sequestration and CH4 production promotion by wollastonite addition in sludge AD. A maximum CH4 yield increment of 30.8% and maximum methane production rate increment of 64.9% with wollastonite addition at dosage of 16.25 g/L were achieved. CO2 was efficient sequestered by wollastonite addition and resulted in a higher CH4 content of 81.7%-82.4%. The mechanism of CO2 sequestration by wollastonite was confirmed as Ca2+ release and subsequently carbonation based on cation and precipitates analysis. The results demonstrated that wollastonite could be applied as an effective additive for simultaneous in-situ CO2 sequestration and CH4 production promotion of sludge AD.