In consideration of the light weight and the impact safety of cars, in recent years, hot stamping has been increasingly applied to the manufacture of car parts, which has driven forward the increasing use of ultra-high strength steel sheet in the automobile industry. However, when the tensile strength of steel is more than about 1200 MPa, the steel sheet is very susceptible to hydrogen induced delayed fracture. Up to now, some research has been carried out on delayed fracture behavior of both high strength and ultra-high strength steel sheet. However, the delayed fracture behavior of a low-carbon Mn-B type steel sheet widely used for hot stamping has not been paid enough attention and fully studied. There are also a scarcity of reports on hydrogen induced delayed fracture behavior of this steel sheet after hot stamping. With the development of the hot stamping, the evaluation of delayed fracture behavior of ultra-high strength steel sheet for hot stamping, especially the delayed fracture behavior of steel sheet after hot stamping has become very urgent. For these reasons, hydrogen induced delayed fracture behavior of a low-carbon Mn-B type ultra-high strength hot stamping steel sheet at both the hot stamped status and the common quenched and tempered status was studied by means of constant load delayed fracture test and hydrogen thermal desorption spectrometry (TDS) analysis. The results show that both the critical delayed fracture stress σ_c and delayed fracture life of the steel sheet after hot stamping process are higher than as-quenched sample, and it even matches the level of the quenched +100℃ tempered sample. Moreover, the σ_c of the steel sheet could be further improved by tempering at 200℃. The delayed fracture surface observed by SEM shows that, under the effect of applied stress and corrosive liquid, the fracture characteristic of the hot stamped sample at crack initiation area changes from brittle intergranular failure in the as-quenched condition to ductile transgranular failure in the hot stamped condition. Furthermore, the TDS result shows that the hydrogen content of steel sheet significantly increases when the steel sheet was applied at critical stress for 100 h in the corrosive liquid. In addition, the hot stamping steel sheet can withstand more hydrogen content than as-quenched sample and quenched +100℃ tempered sample due to the sufficient self tempering. As a result, the hot stamping sample gets a higher critical delayed fracture stress. Therefore, the steel has good delayed fracture resistance after hot stamping, and the delayed fracture resistance of the steel sheet could be further improved by tempering.