In this work, inorganic paste was made from melting slag (MS) of MSWI ash and MSWI bottom ash (MBA) by geopolymer technique. Heavy metals such as Pb and Cu are highly contained in MBA. In the view of environmental protection and resource conservation, recycling of MSWI ash is desirable. MS and MBA were mixed to make inorganic paste. Compressive strength was measured to evaluate the characteristics of inorganic paste after the period of 1, 3 and 7day. Compressive strength of almost 90 MPa was obtained at the mixing ratio of MS : MBA = 9 : 1. And the crystalloid and crystal structure was analyzed by FTIR and XRD. Korea Standard leaching Test (KSLT) is also used to evaluate the environmental safety of inorganic paste. The leached concentration of Pb and Cu were 0.44 ppm and 0.15 ppm, respectively. According to this result, heavy metals were safety immobilized and stabilized.