Fuel cell bus with hydrogen tanks on its roof is different from traditional one. Its mass is greater than traditional one and its centre of gravity is higher, which makes its rollover more easy and dangerous. During the rollover, the great deformation of the body structure will menace the occupants’ safety, and in addition, the hydrogen leaking will threaten the lives of the occupants. So measures should be taken to ensure the deformation of body structure would not hurt the occupants, and the hydrogen pipelines would not have gas leakage. In the light of this objective, the finite element models of fuel cell bus, survive region and anti-intruding region are established, and the simulation of the bus rollover is carried out according to ECER66. The rollover results indicate that the bus is good at resisting the deformation of the rollover, and at the same time it provides data reference for improving the design of fuel cell bus. Furthermore, the pillar intruding coefficient and the clearance between anti-intruding region and tank cover are introduced in the paper to measure the safety abundance ratio of the survival region and the hydrogen pipeline of the fuel cell bus. According to these data, the description of safety of fuel cell bus can be quantified.