Irradiation can be utilized to inhibit sprouting of onions and garlic. Thermoluminescence(TL) is a potential method to detect post-irradiation of onions and garlic because they are irradiated with soil or dusts on them, from which minerals can be isolated for TL analysis. This study was to determine whether TL can be applied for the detection of post-irradiation of onions and garlic. Onions and garlic produced in Korea were irradiated in the range of 0.01~0.6kGy. Minerals isolated from the samples using sodium polytrungstate solution were used for TL analysis. The onions and garlic irradiated at 0.15kGy or higher could be detected with little errors. Minimum dose for the 2nd glow could be applied since the dose for the 2nd glow did not affect the results. The TL intensities of the temperature ranges of 229~295$^{circ}C$ and 229~361$^{circ}C$ and the maximum intensity provided more accurate information for the determination of the post-irradiation of onions and garlic.