Abstract: To elucidate the content of deoxynivalenol( DON) and masked deoxynivalenol( D3G) accumulation and variation in wheat grain. The sterilized wheat grain,with 8 k Gy and 15 k Gy irradiated wheat grain inoculated artificially with Fusarium graminearum strains F-1 and 5035 respectively,were determined by LC- MS / MS after 7,14,21,28 and 35 days of incubation under 25 ℃. The results showed that DON content increased gradually with time in sterilized and 15 k Gy irradiated wheat grain while the content of D3 G were blow limit of detection.The wheat grains can germinate after 8 k Gy irradiation,DON content increased gradually with time in 8 k Gy irradiated wheat grain while the content of D3 G decreased with time. The highest D3 G content was detected in wheat grain incubated after 7 days.The relationship between the ratio of D3 G / DON and incubation time can be well described by exponential model in the conditions of this experiment. R2 of F- 1 and 5035 exponential models regarding the ratio of D3 G / DON and time were 0.97 and 0.93,respectively.As convinced,our results could provide the basis for subsequent studies on the regulatory mechanism of D3 G biosynthesis.