IGZO is a newly developed transparent conducting oxide with higher carrier mobility than traditional materials. In this study, the Hall mobility of distinct surface capping a-IGZO thin films is discussed. The electrical properties of a-IGZO thin films with sheet capping and island capping of calcium were measured, respectively the a-IGZO thin films without surface coating were used as the control group. The resistivity and Hall measurements were undertaken using van der Pauw method. The resistivity (ρ), carrier concentration (n), and Hall mobility (μ) were then calculated from a-IGZO thin films with different types of surface coating. The carrier concentration increases in the thin film with surface coating of calcium. However, the Hall mobility is not improved as predicted.