Abstract: The indium-gallum-tin alloy radiation loop is a new γ-radiation source whichhas quite a few remarkable advantages. In this loop, In-115, captures a thermalneutron in the reactor to preoduce radioisotope In-116 which changes into stableisotope Sn-116 by β-decay. USSR has studied the In-Ga-Sn alloy radiation loopssystematically and accumulated some experiences. For the comprehensive utilizationof the nuclear power station and the nuclear district heating reactor to meet theeverincreasing needs of radiation process industry, research of this new radiationsource in our country is carried out and the fundamental principle materialsstructure operation and safety of the In-Ga-Sn alloy radiation loop and its historyand present condition are discussed briefly.