Electron spin resonance (ESR) spectroscopy is one of the most effective technique for detection of irradiated food containing bone. It was found that the radiation –induced ESR signal (Spectrum,g, factor and peak-to-peak line width ΔH) in bone before and after irradiation was significantly different and could be easily distinguished from the endogenous ESR signal. Sample preparation studies showed vacuumdrying and grinding at frozen temperature was an ideal method. A linear relationship was observed between ESR signal intensity and the absorbed dose (0.3-10.1kGy). It can be proposed that 0.5kGy absorbed doses can be detected by ESR for irradiated food containing bone though detecting sensitivity is very different at the same irradiated dosage with different food such as pork, beef, duck, chicken and fish .The ultimate purpose of this work is to establish a national criterion for detection of irradiated foodstuffs by use of ESR.