Two-dimensional (2D) van der Waals materials have attracted tremendous attention due to their versatile physical properties and flexible manipulation approaches. Among the various types of van der Waals materials, α-In2Se3 is remarkable for its intrinsic 2D ferroelectricity and high-performance opto-electronic properties. However, the study of the α-In2Se3 system in terahertz (THz) radiation is scarce, although it is promising for electrically controlled THz field manipulation. We investigate the α-In2Se3 in different thicknesses and report that the THz generation efficiency induced by femtosecond laser pulses can be largely improved by reducing the thickness from the bulk. Furthermore, we reveal the surge current in thin film coupled with THz emission exhibits a different Auger recombination mode, which is helpful in understanding the mechanism and provides insights into the design of 2D highly efficient THz devices.