Abstract For the first time, we found by EHEED that a part of indium adatoms on the Si(lll) surface transports easily under the influence of an applied dc electric field. According to the observation of the surface electromigration process, it is shown that the states of adsorption of indium atoms on a clean Si (111) surface can be characterized as two phases - the first interface layer bound to silicon surface tightly is hardly affected by a electric field, it is called the tightly bound layer; overlayers on the first layer bound to the first interface layer loosely, can transport along the direction of an applied electric field, they are called transport layers. From the temperature dependence of the transport mobility, we find that the activation energy of surface electromigration is △H = 0.43 eV.The charge transfer in the process of In-Si(111) interface formation has been investigated by measurements of the surface conductance. The results show that indium atom is adsorbed as surface deep donor. Surface electromigration is attributed to Coulomb force applied on the ionized indium atom.