In this paper, the results of the thermal and infra-red analysis of Dy substituted in Bi (Pb)-2223 superconductor have been studied by thermogravimetric (TG) and Fourier transform infrared (FTIR). The samples with nominal composition of Bi1.6Pb0.4Sr2Ca2-xDyxCu3Oy where x = 0.000, 0.025, 0.050, 0.100, and 0.200 were prepared by co-precipitation (COP) method using metal acetate as the starting salts. The mechanism of thermal analysis of the precursor powder for each stage (drying, precalcine, and calcine) were studied from 20 °C to 920 °C by 5 °C/min of heating rate. Interestingly, the thermal decomposition proceeds in the almost similar way regardless of the Dy substitution level with five major drops at the drying stage. Based on TG curves results, the temperature range from 840 °C to 850 °C can be suggested as an optimum calcination and sintering temperature. The majority of decomposition step which related to the loss of water from oxalate was in the range of 100 °C to 200 °C while the formation of precipitation into Bi2O3, PbO, SrCO3, CaCO3, CuO, and Dy2O3 were in the range of 210 °C to 360 °C. From the FTIR result, all the precursor powders qualitatively showed four main regions and the existence of –OH group can increase the diffusion rate between metals during the synthesis process.