Abstract: Based on the composition of In-Sn binary eutectic point and using Bi as a substitute for In,a low melting point alloy for green thermal cutoff was developed and the interrelation of the composition,microstructure and melting point,action temperature and manufacture feasibility of the alloy was investigated.The results indicated that with the substitution of Bi in In,a green thermal cutoff which meets the demands of environmental protection could be made from the alloy.