The ancient bronze arrows made in late Spring-Autumn Warring States Period in the middle Yangtse River region were examined by using scanning electron microscopic（SEM）

energy-disperse spectrometer（EDS） and microhardness tester.It was found that according to the degree of rust-eaten

the arrow microstructure was composed of three distinction layers including completely mineralized layer which exhibited the loosest morphology and the lowest hardness

transition layer and core original material.In addition

different regions showed variant rust-eaten degree due to the environmental conditions.Two types of micro-cracks were also observed from the cross-section of the arrows.The one was the result of expansion in the mineralized layer when the environmental temperature and humidity changed which further gradual development would finally induce a so-called "powder rusty".The other was the result of the low toughness and deformability in cylindrical arrow cross-section.