Due to the high integration and high speed, Power-Ground (P/G) network design becomes a critical challenge in mobile IC package. As accurate IR-drop analysis provides important reference for P/G network design, an electro-thermal coanalysis flow is presented in this paper to obtain accurate IRdrop distribution of a low-power mobile IC package. In this analysis process, the change of temperature-dependent leakage power caused by device heating and self-heating is considered when IR-drop analysis is performed, which has seriously impact on IR-drop. In this paper, a two-layer high-density FCBGA (Flip Chip Ball Grid Array) package is used for analysis and the simulation result shows that the IR-drop on package increases by 16.1% when considering leakage power and self-heating.